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Comparing AnyEvent/README (file contents):
Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs.
Revision 1.48 by root, Sun Jul 26 00:17:24 2009 UTC

…		…
1	NAME	1	NAME
2	AnyEvent - provide framework for multiple event loops	2	AnyEvent - the DBI of event loop programming
3		3
4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event	4	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, IO::Async, Qt and POE are
5	loops	5	various supported event loops/environments.
6		6
7	SYNOPSIS	7	SYNOPSIS
8	use AnyEvent;	8	use AnyEvent;
9		9
		10	# file descriptor readable
10	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub { ... });	11	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
11		12
		13	# one-shot or repeating timers
12	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });	14	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
13	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...	15	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
14		16
15	print AnyEvent->now; # prints current event loop time	17	print AnyEvent->now; # prints current event loop time
16	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.	18	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
17		19
		20	# POSIX signal
18	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });	21	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
19		22
		23	# child process exit
20	my $w = AnyEvent->child (pid => $pid, cb => sub {	24	my $w = AnyEvent->child (pid => $pid, cb => sub {
21	my ($pid, $status) = @_;	25	my ($pid, $status) = @_;
22	...	26	...
23	});	27	});
		28
		29	# called when event loop idle (if applicable)
		30	my $w = AnyEvent->idle (cb => sub { ... });
24		31
25	my $w = AnyEvent->condvar; # stores whether a condition was flagged	32	my $w = AnyEvent->condvar; # stores whether a condition was flagged
26	$w->send; # wake up current and all future recv's	33	$w->send; # wake up current and all future recv's
27	$w->recv; # enters "main loop" till $condvar gets ->send	34	$w->recv; # enters "main loop" till $condvar gets ->send
28	# use a condvar in callback mode:	35	# use a condvar in callback mode:
30		37
31	INTRODUCTION/TUTORIAL	38	INTRODUCTION/TUTORIAL
32	This manpage is mainly a reference manual. If you are interested in a	39	This manpage is mainly a reference manual. If you are interested in a
33	tutorial or some gentle introduction, have a look at the AnyEvent::Intro	40	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
34	manpage.	41	manpage.
		42
		43	SUPPORT
		44	There is a mailinglist for discussing all things AnyEvent, and an IRC
		45	channel, too.
		46
		47	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
		48	Repository, at <http://anyevent.schmorp.de>, for more info.
35		49
36	WHY YOU SHOULD USE THIS MODULE (OR NOT)	50	WHY YOU SHOULD USE THIS MODULE (OR NOT)
37	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	51	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
38	nowadays. So what is different about AnyEvent?	52	nowadays. So what is different about AnyEvent?
39		53
…		…
162		176
163	I/O WATCHERS	177	I/O WATCHERS
164	You can create an I/O watcher by calling the "AnyEvent->io" method with	178	You can create an I/O watcher by calling the "AnyEvent->io" method with
165	the following mandatory key-value pairs as arguments:	179	the following mandatory key-value pairs as arguments:
166		180
167	"fh" is the Perl file handle (not file descriptor) to watch for	181	"fh" is the Perl file handle (or a naked file descriptor) to watch for
168	events (AnyEvent might or might not keep a reference to this file	182	events (AnyEvent might or might not keep a reference to this file
169	handle). Note that only file handles pointing to things for which	183	handle). Note that only file handles pointing to things for which
170	non-blocking operation makes sense are allowed. This includes sockets,	184	non-blocking operation makes sense are allowed. This includes sockets,
171	most character devices, pipes, fifos and so on, but not for example	185	most character devices, pipes, fifos and so on, but not for example
172	files or block devices.	186	files or block devices.
…		…
343	invocation, and callback invocation will be synchronous. Synchronous	357	invocation, and callback invocation will be synchronous. Synchronous
344	means that it might take a while until the signal gets handled by the	358	means that it might take a while until the signal gets handled by the
345	process, but it is guaranteed not to interrupt any other callbacks.	359	process, but it is guaranteed not to interrupt any other callbacks.
346		360
347	The main advantage of using these watchers is that you can share a	361	The main advantage of using these watchers is that you can share a
348	signal between multiple watchers.	362	signal between multiple watchers, and AnyEvent will ensure that signals
		363	will not interrupt your program at bad times.
349		364
350	This watcher might use %SIG, so programs overwriting those signals	365	This watcher might use %SIG (depending on the event loop used), so
351	directly will likely not work correctly.	366	programs overwriting those signals directly will likely not work
		367	correctly.
352		368
353	Example: exit on SIGINT	369	Example: exit on SIGINT
354		370
355	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	371	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		372
		373	Signal Races, Delays and Workarounds
		374	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		375	callbacks to signals in a generic way, which is a pity, as you cannot do
		376	race-free signal handling in perl. AnyEvent will try to do it's best,
		377	but in some cases, signals will be delayed. The maximum time a signal
		378	might be delayed is specified in $AnyEvent::MAX_SIGNAL_LATENCY (default:
		379	10 seconds). This variable can be changed only before the first signal
		380	watcher is created, and should be left alone otherwise. Higher values
		381	will cause fewer spurious wake-ups, which is better for power and CPU
		382	saving. All these problems can be avoided by installing the optional
		383	Async::Interrupt module. This will not work with inherently broken event
		384	loops such as Event or Event::Lib (and not with POE currently, as POE
		385	does it's own workaround with one-second latency). With those, you just
		386	have to suffer the delays.
356		387
357	CHILD PROCESS WATCHERS	388	CHILD PROCESS WATCHERS
358	You can also watch on a child process exit and catch its exit status.	389	You can also watch on a child process exit and catch its exit status.
359		390
360	The child process is specified by the "pid" argument (if set to 0, it	391	The child process is specified by the "pid" argument (one some backends,
361	watches for any child process exit). The watcher will triggered only	392	using 0 watches for any child process exit, on others this will croak).
362	when the child process has finished and an exit status is available, not	393	The watcher will be triggered only when the child process has finished
363	on any trace events (stopped/continued).	394	and an exit status is available, not on any trace events
		395	(stopped/continued).
364		396
365	The callback will be called with the pid and exit status (as returned by	397	The callback will be called with the pid and exit status (as returned by
366	waitpid), so unlike other watcher types, you can rely on child watcher	398	waitpid), so unlike other watcher types, you can rely on child watcher
367	callback arguments.	399	callback arguments.
368		400
…		…
373		405
374	There is a slight catch to child watchers, however: you usually start	406	There is a slight catch to child watchers, however: you usually start
375	them after the child process was created, and this means the process	407	them after the child process was created, and this means the process
376	could have exited already (and no SIGCHLD will be sent anymore).	408	could have exited already (and no SIGCHLD will be sent anymore).
377		409
378	Not all event models handle this correctly (POE doesn't), but even for	410	Not all event models handle this correctly (neither POE nor IO::Async
		411	do, see their AnyEvent::Impl manpages for details), but even for event
379	event models that do handle this correctly, they usually need to be	412	models that do handle this correctly, they usually need to be loaded
380	loaded before the process exits (i.e. before you fork in the first	413	before the process exits (i.e. before you fork in the first place).
381	place).	414	AnyEvent's pure perl event loop handles all cases correctly regardless
		415	of when you start the watcher.
382		416
383	This means you cannot create a child watcher as the very first thing in	417	This means you cannot create a child watcher as the very first thing in
384	an AnyEvent program, you have to create at least one watcher before	418	an AnyEvent program, you have to create at least one watcher before
385	you "fork" the child (alternatively, you can call "AnyEvent::detect").	419	you "fork" the child (alternatively, you can call "AnyEvent::detect").
386		420
		421	As most event loops do not support waiting for child events, they will
		422	be emulated by AnyEvent in most cases, in which the latency and race
		423	problems mentioned in the description of signal watchers apply.
		424
387	Example: fork a process and wait for it	425	Example: fork a process and wait for it
388		426
389	my $done = AnyEvent->condvar;	427	my $done = AnyEvent->condvar;
390		428
391	my $pid = fork or exit 5;	429	my $pid = fork or exit 5;
392		430
393	my $w = AnyEvent->child (	431	my $w = AnyEvent->child (
394	pid => $pid,	432	pid => $pid,
395	cb => sub {	433	cb => sub {
396	my ($pid, $status) = @_;	434	my ($pid, $status) = @_;
397	warn "pid $pid exited with status $status";	435	warn "pid $pid exited with status $status";
398	$done->send;	436	$done->send;
399	},	437	},
400	);	438	);
401		439
402	# do something else, then wait for process exit	440	# do something else, then wait for process exit
403	$done->recv;	441	$done->recv;
		442
		443	IDLE WATCHERS
		444	Sometimes there is a need to do something, but it is not so important to
		445	do it instantly, but only when there is nothing better to do. This
		446	"nothing better to do" is usually defined to be "no other events need
		447	attention by the event loop".
		448
		449	Idle watchers ideally get invoked when the event loop has nothing better
		450	to do, just before it would block the process to wait for new events.
		451	Instead of blocking, the idle watcher is invoked.
		452
		453	Most event loops unfortunately do not really support idle watchers (only
		454	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		455	will simply call the callback "from time to time".
		456
		457	Example: read lines from STDIN, but only process them when the program
		458	is otherwise idle:
		459
		460	my @lines; # read data
		461	my $idle_w;
		462	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		463	push @lines, scalar <STDIN>;
		464
		465	# start an idle watcher, if not already done
		466	$idle_w \|\|= AnyEvent->idle (cb => sub {
		467	# handle only one line, when there are lines left
		468	if (my $line = shift @lines) {
		469	print "handled when idle: $line";
		470	} else {
		471	# otherwise disable the idle watcher again
		472	undef $idle_w;
		473	}
		474	});
		475	});
404		476
405	CONDITION VARIABLES	477	CONDITION VARIABLES
406	If you are familiar with some event loops you will know that all of them	478	If you are familiar with some event loops you will know that all of them
407	require you to run some blocking "loop", "run" or similar function that	479	require you to run some blocking "loop", "run" or similar function that
408	will actively watch for new events and call your callbacks.	480	will actively watch for new events and call your callbacks.
409		481
410	AnyEvent is different, it expects somebody else to run the event loop	482	AnyEvent is slightly different: it expects somebody else to run the
411	and will only block when necessary (usually when told by the user).	483	event loop and will only block when necessary (usually when told by the
		484	user).
412		485
413	The instrument to do that is called a "condition variable", so called	486	The instrument to do that is called a "condition variable", so called
414	because they represent a condition that must become true.	487	because they represent a condition that must become true.
415		488
		489	Now is probably a good time to look at the examples further below.
		490
416	Condition variables can be created by calling the "AnyEvent->condvar"	491	Condition variables can be created by calling the "AnyEvent->condvar"
417	method, usually without arguments. The only argument pair allowed is	492	method, usually without arguments. The only argument pair allowed is
418
419	"cb", which specifies a callback to be called when the condition	493	"cb", which specifies a callback to be called when the condition
420	variable becomes true, with the condition variable as the first argument	494	variable becomes true, with the condition variable as the first argument
421	(but not the results).	495	(but not the results).
422		496
423	After creation, the condition variable is "false" until it becomes	497	After creation, the condition variable is "false" until it becomes
…		…
428	Condition variables are similar to callbacks, except that you can	502	Condition variables are similar to callbacks, except that you can
429	optionally wait for them. They can also be called merge points - points	503	optionally wait for them. They can also be called merge points - points
430	in time where multiple outstanding events have been processed. And yet	504	in time where multiple outstanding events have been processed. And yet
431	another way to call them is transactions - each condition variable can	505	another way to call them is transactions - each condition variable can
432	be used to represent a transaction, which finishes at some point and	506	be used to represent a transaction, which finishes at some point and
433	delivers a result.	507	delivers a result. And yet some people know them as "futures" - a
		508	promise to compute/deliver something that you can wait for.
434		509
435	Condition variables are very useful to signal that something has	510	Condition variables are very useful to signal that something has
436	finished, for example, if you write a module that does asynchronous http	511	finished, for example, if you write a module that does asynchronous http
437	requests, then a condition variable would be the ideal candidate to	512	requests, then a condition variable would be the ideal candidate to
438	signal the availability of results. The user can either act when the	513	signal the availability of results. The user can either act when the
…		…
472	after => 1,	547	after => 1,
473	cb => sub { $result_ready->send },	548	cb => sub { $result_ready->send },
474	);	549	);
475		550
476	# this "blocks" (while handling events) till the callback	551	# this "blocks" (while handling events) till the callback
477	# calls send	552	# calls -<send
478	$result_ready->recv;	553	$result_ready->recv;
479		554
480	Example: wait for a timer, but take advantage of the fact that condition	555	Example: wait for a timer, but take advantage of the fact that condition
481	variables are also code references.	556	variables are also callable directly.
482		557
483	my $done = AnyEvent->condvar;	558	my $done = AnyEvent->condvar;
484	my $delay = AnyEvent->timer (after => 5, cb => $done);	559	my $delay = AnyEvent->timer (after => 5, cb => $done);
485	$done->recv;	560	$done->recv;
486		561
…		…
492		567
493	...	568	...
494		569
495	my @info = $couchdb->info->recv;	570	my @info = $couchdb->info->recv;
496		571
497	And this is how you would just ste a callback to be called whenever the	572	And this is how you would just set a callback to be called whenever the
498	results are available:	573	results are available:
499		574
500	$couchdb->info->cb (sub {	575	$couchdb->info->cb (sub {
501	my @info = $_[0]->recv;	576	my @info = $_[0]->recv;
502	});	577	});
…		…
517		592
518	Any arguments passed to the "send" call will be returned by all	593	Any arguments passed to the "send" call will be returned by all
519	future "->recv" calls.	594	future "->recv" calls.
520		595
521	Condition variables are overloaded so one can call them directly (as	596	Condition variables are overloaded so one can call them directly (as
522	a code reference). Calling them directly is the same as calling	597	if they were a code reference). Calling them directly is the same as
523	"send". Note, however, that many C-based event loops do not handle	598	calling "send".
524	overloading, so as tempting as it may be, passing a condition
525	variable instead of a callback does not work. Both the pure perl and
526	EV loops support overloading, however, as well as all functions that
527	use perl to invoke a callback (as in AnyEvent::Socket and
528	AnyEvent::DNS for example).
529		599
530	$cv->croak ($error)	600	$cv->croak ($error)
531	Similar to send, but causes all call's to "->recv" to invoke	601	Similar to send, but causes all call's to "->recv" to invoke
532	"Carp::croak" with the given error message/object/scalar.	602	"Carp::croak" with the given error message/object/scalar.
533		603
534	This can be used to signal any errors to the condition variable	604	This can be used to signal any errors to the condition variable
535	user/consumer.	605	user/consumer. Doing it this way instead of calling "croak" directly
		606	delays the error detetcion, but has the overwhelmign advantage that
		607	it diagnoses the error at the place where the result is expected,
		608	and not deep in some event clalback without connection to the actual
		609	code causing the problem.
536		610
537	$cv->begin ([group callback])	611	$cv->begin ([group callback])
538	$cv->end	612	$cv->end
539	These two methods are EXPERIMENTAL and MIGHT CHANGE.
540
541	These two methods can be used to combine many transactions/events	613	These two methods can be used to combine many transactions/events
542	into one. For example, a function that pings many hosts in parallel	614	into one. For example, a function that pings many hosts in parallel
543	might want to use a condition variable for the whole process.	615	might want to use a condition variable for the whole process.
544		616
545	Every call to "->begin" will increment a counter, and every call to	617	Every call to "->begin" will increment a counter, and every call to
546	"->end" will decrement it. If the counter reaches 0 in "->end", the	618	"->end" will decrement it. If the counter reaches 0 in "->end", the
547	(last) callback passed to "begin" will be executed. That callback is	619	(last) callback passed to "begin" will be executed. That callback is
548	supposed to call "->send", but that is not required. If no	620	supposed to call "->send", but that is not required. If no
549	callback was set, "send" will be called without any arguments.	621	callback was set, "send" will be called without any arguments.
550		622
551	Let's clarify this with the ping example:	623	You can think of "$cv->send" giving you an OR condition (one call
		624	sends), while "$cv->begin" and "$cv->end" giving you an AND
		625	condition (all "begin" calls must be "end"'ed before the condvar
		626	sends).
		627
		628	Let's start with a simple example: you have two I/O watchers (for
		629	example, STDOUT and STDERR for a program), and you want to wait for
		630	both streams to close before activating a condvar:
		631
		632	my $cv = AnyEvent->condvar;
		633
		634	$cv->begin; # first watcher
		635	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		636	defined sysread $fh1, my $buf, 4096
		637	or $cv->end;
		638	});
		639
		640	$cv->begin; # second watcher
		641	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		642	defined sysread $fh2, my $buf, 4096
		643	or $cv->end;
		644	});
		645
		646	$cv->recv;
		647
		648	This works because for every event source (EOF on file handle),
		649	there is one call to "begin", so the condvar waits for all calls to
		650	"end" before sending.
		651
		652	The ping example mentioned above is slightly more complicated, as
		653	the there are results to be passwd back, and the number of tasks
		654	that are begung can potentially be zero:
552		655
553	my $cv = AnyEvent->condvar;	656	my $cv = AnyEvent->condvar;
554		657
555	my %result;	658	my %result;
556	$cv->begin (sub { $cv->send (\%result) });	659	$cv->begin (sub { $cv->send (\%result) });
…		…
576	the loop, which serves two important purposes: first, it sets the	679	the loop, which serves two important purposes: first, it sets the
577	callback to be called once the counter reaches 0, and second, it	680	callback to be called once the counter reaches 0, and second, it
578	ensures that "send" is called even when "no" hosts are being pinged	681	ensures that "send" is called even when "no" hosts are being pinged
579	(the loop doesn't execute once).	682	(the loop doesn't execute once).
580		683
581	This is the general pattern when you "fan out" into multiple	684	This is the general pattern when you "fan out" into multiple (but
582	subrequests: use an outer "begin"/"end" pair to set the callback and	685	potentially none) subrequests: use an outer "begin"/"end" pair to
583	ensure "end" is called at least once, and then, for each subrequest	686	set the callback and ensure "end" is called at least once, and then,
584	you start, call "begin" and for each subrequest you finish, call	687	for each subrequest you start, call "begin" and for each subrequest
585	"end".	688	you finish, call "end".
586		689
587	METHODS FOR CONSUMERS	690	METHODS FOR CONSUMERS
588	These methods should only be used by the consuming side, i.e. the code	691	These methods should only be used by the consuming side, i.e. the code
589	awaits the condition.	692	awaits the condition.
590		693
…		…
599	function will call "croak".	702	function will call "croak".
600		703
601	In list context, all parameters passed to "send" will be returned,	704	In list context, all parameters passed to "send" will be returned,
602	in scalar context only the first one will be returned.	705	in scalar context only the first one will be returned.
603		706
		707	Note that doing a blocking wait in a callback is not supported by
		708	any event loop, that is, recursive invocation of a blocking "->recv"
		709	is not allowed, and the "recv" call will "croak" if such a condition
		710	is detected. This condition can be slightly loosened by using
		711	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		712	thread that doesn't run the event loop itself.
		713
604	Not all event models support a blocking wait - some die in that case	714	Not all event models support a blocking wait - some die in that case
605	(programs might want to do that to stay interactive), so *if you are	715	(programs might want to do that to stay interactive), so *if you are
606	using this from a module, never require a blocking wait*, but let	716	using this from a module, never require a blocking wait*. Instead,
607	the caller decide whether the call will block or not (for example,	717	let the caller decide whether the call will block or not (for
608	by coupling condition variables with some kind of request results	718	example, by coupling condition variables with some kind of request
609	and supporting callbacks so the caller knows that getting the result	719	results and supporting callbacks so the caller knows that getting
610	will not block, while still supporting blocking waits if the caller	720	the result will not block, while still supporting blocking waits if
611	so desires).	721	the caller so desires).
612
613	Another reason never to "->recv" in a module is that you cannot
614	sensibly have two "->recv"'s in parallel, as that would require
615	multiple interpreters or coroutines/threads, none of which
616	"AnyEvent" can supply.
617
618	The Coro module, however, can and does supply coroutines and, in
619	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
620	versions and also integrates coroutines into AnyEvent, making
621	blocking "->recv" calls perfectly safe as long as they are done from
622	another coroutine (one that doesn't run the event loop).
623		722
624	You can ensure that "-recv" never blocks by setting a callback and	723	You can ensure that "-recv" never blocks by setting a callback and
625	only calling "->recv" from within that callback (or at a later	724	only calling "->recv" from within that callback (or at a later
626	time). This will work even when the event loop does not support	725	time). This will work even when the event loop does not support
627	blocking waits otherwise.	726	blocking waits otherwise.
…		…
637	The callback will be called when the condition becomes "true", i.e.	736	The callback will be called when the condition becomes "true", i.e.
638	when "send" or "croak" are called, with the only argument being the	737	when "send" or "croak" are called, with the only argument being the
639	condition variable itself. Calling "recv" inside the callback or at	738	condition variable itself. Calling "recv" inside the callback or at
640	any later time is guaranteed not to block.	739	any later time is guaranteed not to block.
641		740
		741	SUPPORTED EVENT LOOPS/BACKENDS
		742	The available backend classes are (every class has its own manpage):
		743
		744	Backends that are autoprobed when no other event loop can be found.
		745	EV is the preferred backend when no other event loop seems to be in
		746	use. If EV is not installed, then AnyEvent will try Event, and,
		747	failing that, will fall back to its own pure-perl implementation,
		748	which is available everywhere as it comes with AnyEvent itself.
		749
		750	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		751	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		752	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		753
		754	Backends that are transparently being picked up when they are used.
		755	These will be used when they are currently loaded when the first
		756	watcher is created, in which case it is assumed that the application
		757	is using them. This means that AnyEvent will automatically pick the
		758	right backend when the main program loads an event module before
		759	anything starts to create watchers. Nothing special needs to be done
		760	by the main program.
		761
		762	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		763	AnyEvent::Impl::Tk based on Tk, very broken.
		764	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		765	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		766	AnyEvent::Impl::Irssi used when running within irssi.
		767
		768	Backends with special needs.
		769	Qt requires the Qt::Application to be instantiated first, but will
		770	otherwise be picked up automatically. As long as the main program
		771	instantiates the application before any AnyEvent watchers are
		772	created, everything should just work.
		773
		774	AnyEvent::Impl::Qt based on Qt.
		775
		776	Support for IO::Async can only be partial, as it is too broken and
		777	architecturally limited to even support the AnyEvent API. It also is
		778	the only event loop that needs the loop to be set explicitly, so it
		779	can only be used by a main program knowing about AnyEvent. See
		780	AnyEvent::Impl::Async for the gory details.
		781
		782	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		783
		784	Event loops that are indirectly supported via other backends.
		785	Some event loops can be supported via other modules:
		786
		787	There is no direct support for WxWidgets (Wx) or Prima.
		788
		789	WxWidgets has no support for watching file handles. However, you can
		790	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		791	simply polls 20 times per second, which was considered to be too
		792	horrible to even consider for AnyEvent.
		793
		794	Prima is not supported as nobody seems to be using it, but it has a
		795	POE backend, so it can be supported through POE.
		796
		797	AnyEvent knows about both Prima and Wx, however, and will try to
		798	load POE when detecting them, in the hope that POE will pick them
		799	up, in which case everything will be automatic.
		800
642	GLOBAL VARIABLES AND FUNCTIONS	801	GLOBAL VARIABLES AND FUNCTIONS
		802	These are not normally required to use AnyEvent, but can be useful to
		803	write AnyEvent extension modules.
		804
643	$AnyEvent::MODEL	805	$AnyEvent::MODEL
644	Contains "undef" until the first watcher is being created. Then it	806	Contains "undef" until the first watcher is being created, before
		807	the backend has been autodetected.
		808
645	contains the event model that is being used, which is the name of	809	Afterwards it contains the event model that is being used, which is
646	the Perl class implementing the model. This class is usually one of	810	the name of the Perl class implementing the model. This class is
647	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	811	usually one of the "AnyEvent::Impl:xxx" modules, but can be any
648	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).	812	other class in the case AnyEvent has been extended at runtime (e.g.
649		813	in rxvt-unicode it will be "urxvt::anyevent").
650	The known classes so far are:
651
652	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
653	AnyEvent::Impl::Event based on Event, second best choice.
654	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
655	AnyEvent::Impl::Glib based on Glib, third-best choice.
656	AnyEvent::Impl::Tk based on Tk, very bad choice.
657	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
658	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
659	AnyEvent::Impl::POE based on POE, not generic enough for full support.
660
661	There is no support for WxWidgets, as WxWidgets has no support for
662	watching file handles. However, you can use WxWidgets through the
663	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
664	second, which was considered to be too horrible to even consider for
665	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
666	using it's adaptor.
667
668	AnyEvent knows about Prima and Wx and will try to use POE when
669	autodetecting them.
670		814
671	AnyEvent::detect	815	AnyEvent::detect
672	Returns $AnyEvent::MODEL, forcing autodetection of the event model	816	Returns $AnyEvent::MODEL, forcing autodetection of the event model
673	if necessary. You should only call this function right before you	817	if necessary. You should only call this function right before you
674	would have created an AnyEvent watcher anyway, that is, as late as	818	would have created an AnyEvent watcher anyway, that is, as late as
675	possible at runtime.	819	possible at runtime, and not e.g. while initialising of your module.
		820
		821	If you need to do some initialisation before AnyEvent watchers are
		822	created, use "post_detect".
676		823
677	$guard = AnyEvent::post_detect { BLOCK }	824	$guard = AnyEvent::post_detect { BLOCK }
678	Arranges for the code block to be executed as soon as the event	825	Arranges for the code block to be executed as soon as the event
679	model is autodetected (or immediately if this has already happened).	826	model is autodetected (or immediately if this has already happened).
680		827
		828	The block will be executed after the actual backend has been
		829	detected ($AnyEvent::MODEL is set), but before any watchers have
		830	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		831	other initialisations - see the sources of AnyEvent::Strict or
		832	AnyEvent::AIO to see how this is used.
		833
		834	The most common usage is to create some global watchers, without
		835	forcing event module detection too early, for example, AnyEvent::AIO
		836	creates and installs the global IO::AIO watcher in a "post_detect"
		837	block to avoid autodetecting the event module at load time.
		838
681	If called in scalar or list context, then it creates and returns an	839	If called in scalar or list context, then it creates and returns an
682	object that automatically removes the callback again when it is	840	object that automatically removes the callback again when it is
		841	destroyed (or "undef" when the hook was immediately executed). See
683	destroyed. See Coro::BDB for a case where this is useful.	842	AnyEvent::AIO for a case where this is useful.
		843
		844	Example: Create a watcher for the IO::AIO module and store it in
		845	$WATCHER. Only do so after the event loop is initialised, though.
		846
		847	our WATCHER;
		848
		849	my $guard = AnyEvent::post_detect {
		850	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		851	};
		852
		853	# the \|\|= is important in case post_detect immediately runs the block,
		854	# as to not clobber the newly-created watcher. assigning both watcher and
		855	# post_detect guard to the same variable has the advantage of users being
		856	# able to just C<undef $WATCHER> if the watcher causes them grief.
		857
		858	$WATCHER \|\|= $guard;
684		859
685	@AnyEvent::post_detect	860	@AnyEvent::post_detect
686	If there are any code references in this array (you can "push" to it	861	If there are any code references in this array (you can "push" to it
687	before or after loading AnyEvent), then they will called directly	862	before or after loading AnyEvent), then they will called directly
688	after the event loop has been chosen.	863	after the event loop has been chosen.
689		864
690	You should check $AnyEvent::MODEL before adding to this array,	865	You should check $AnyEvent::MODEL before adding to this array,
691	though: if it contains a true value then the event loop has already	866	though: if it is defined then the event loop has already been
692	been detected, and the array will be ignored.	867	detected, and the array will be ignored.
693		868
694	Best use "AnyEvent::post_detect { BLOCK }" instead.	869	Best use "AnyEvent::post_detect { BLOCK }" when your application
		870	allows it,as it takes care of these details.
		871
		872	This variable is mainly useful for modules that can do something
		873	useful when AnyEvent is used and thus want to know when it is
		874	initialised, but do not need to even load it by default. This array
		875	provides the means to hook into AnyEvent passively, without loading
		876	it.
695		877
696	WHAT TO DO IN A MODULE	878	WHAT TO DO IN A MODULE
697	As a module author, you should "use AnyEvent" and call AnyEvent methods	879	As a module author, you should "use AnyEvent" and call AnyEvent methods
698	freely, but you should not load a specific event module or rely on it.	880	freely, but you should not load a specific event module or rely on it.
699		881
…		…
750	variable somewhere, waiting for it, and sending it when the program	932	variable somewhere, waiting for it, and sending it when the program
751	should exit cleanly.	933	should exit cleanly.
752		934
753	OTHER MODULES	935	OTHER MODULES
754	The following is a non-exhaustive list of additional modules that use	936	The following is a non-exhaustive list of additional modules that use
755	AnyEvent and can therefore be mixed easily with other AnyEvent modules	937	AnyEvent as a client and can therefore be mixed easily with other
756	in the same program. Some of the modules come with AnyEvent, some are	938	AnyEvent modules and other event loops in the same program. Some of the
757	available via CPAN.	939	modules come with AnyEvent, most are available via CPAN.
758		940
759	AnyEvent::Util	941	AnyEvent::Util
760	Contains various utility functions that replace often-used but	942	Contains various utility functions that replace often-used but
761	blocking functions such as "inet_aton" by event-/callback-based	943	blocking functions such as "inet_aton" by event-/callback-based
762	versions.	944	versions.
…		…
768	more.	950	more.
769		951
770	AnyEvent::Handle	952	AnyEvent::Handle
771	Provide read and write buffers, manages watchers for reads and	953	Provide read and write buffers, manages watchers for reads and
772	writes, supports raw and formatted I/O, I/O queued and fully	954	writes, supports raw and formatted I/O, I/O queued and fully
773	transparent and non-blocking SSL/TLS.	955	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
774		956
775	AnyEvent::DNS	957	AnyEvent::DNS
776	Provides rich asynchronous DNS resolver capabilities.	958	Provides rich asynchronous DNS resolver capabilities.
777		959
778	AnyEvent::HTTP	960	AnyEvent::HTTP
…		…
799		981
800	AnyEvent::GPSD	982	AnyEvent::GPSD
801	A non-blocking interface to gpsd, a daemon delivering GPS	983	A non-blocking interface to gpsd, a daemon delivering GPS
802	information.	984	information.
803		985
		986	AnyEvent::IRC
		987	AnyEvent based IRC client module family (replacing the older
		988	Net::IRC3).
		989
		990	AnyEvent::XMPP
		991	AnyEvent based XMPP (Jabber protocol) module family (replacing the
		992	older Net::XMPP2>.
		993
804	AnyEvent::IGS	994	AnyEvent::IGS
805	A non-blocking interface to the Internet Go Server protocol (used by	995	A non-blocking interface to the Internet Go Server protocol (used by
806	App::IGS).	996	App::IGS).
807		997
808	AnyEvent::IRC
809	AnyEvent based IRC client module family (replacing the older
810	Net::IRC3).
811
812	Net::XMPP2
813	AnyEvent based XMPP (Jabber protocol) module family.
814
815	Net::FCP	998	Net::FCP
816	AnyEvent-based implementation of the Freenet Client Protocol,	999	AnyEvent-based implementation of the Freenet Client Protocol,
817	birthplace of AnyEvent.	1000	birthplace of AnyEvent.
818		1001
819	Event::ExecFlow	1002	Event::ExecFlow
820	High level API for event-based execution flow control.	1003	High level API for event-based execution flow control.
821		1004
822	Coro	1005	Coro
823	Has special support for AnyEvent via Coro::AnyEvent.	1006	Has special support for AnyEvent via Coro::AnyEvent.
824
825	IO::Lambda
826	The lambda approach to I/O - don't ask, look there. Can use
827	AnyEvent.
828		1007
829	ERROR AND EXCEPTION HANDLING	1008	ERROR AND EXCEPTION HANDLING
830	In general, AnyEvent does not do any error handling - it relies on the	1009	In general, AnyEvent does not do any error handling - it relies on the
831	caller to do that if required. The AnyEvent::Strict module (see also the	1010	caller to do that if required. The AnyEvent::Strict module (see also the
832	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1011	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
842	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1021	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
843	Glib uses "install_exception_handler" and so on.	1022	Glib uses "install_exception_handler" and so on.
844		1023
845	ENVIRONMENT VARIABLES	1024	ENVIRONMENT VARIABLES
846	The following environment variables are used by this module or its	1025	The following environment variables are used by this module or its
847	submodules:	1026	submodules.
		1027
		1028	Note that AnyEvent will remove all environment variables starting with
		1029	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1030	enabled.
848		1031
849	"PERL_ANYEVENT_VERBOSE"	1032	"PERL_ANYEVENT_VERBOSE"
850	By default, AnyEvent will be completely silent except in fatal	1033	By default, AnyEvent will be completely silent except in fatal
851	conditions. You can set this environment variable to make AnyEvent	1034	conditions. You can set this environment variable to make AnyEvent
852	more talkative.	1035	more talkative.
…		…
855	conditions, such as not being able to load the event model specified	1038	conditions, such as not being able to load the event model specified
856	by "PERL_ANYEVENT_MODEL".	1039	by "PERL_ANYEVENT_MODEL".
857		1040
858	When set to 2 or higher, cause AnyEvent to report to STDERR which	1041	When set to 2 or higher, cause AnyEvent to report to STDERR which
859	event model it chooses.	1042	event model it chooses.
		1043
		1044	When set to 8 or higher, then AnyEvent will report extra information
		1045	on which optional modules it loads and how it implements certain
		1046	features.
860		1047
861	"PERL_ANYEVENT_STRICT"	1048	"PERL_ANYEVENT_STRICT"
862	AnyEvent does not do much argument checking by default, as thorough	1049	AnyEvent does not do much argument checking by default, as thorough
863	argument checking is very costly. Setting this variable to a true	1050	argument checking is very costly. Setting this variable to a true
864	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1051	value will cause AnyEvent to load "AnyEvent::Strict" and then to
865	thoroughly check the arguments passed to most method calls. If it	1052	thoroughly check the arguments passed to most method calls. If it
866	finds any problems it will croak.	1053	finds any problems, it will croak.
867		1054
868	In other words, enables "strict" mode.	1055	In other words, enables "strict" mode.
869		1056
870	Unlike "use strict", it is definitely recommended ot keep it off in	1057	Unlike "use strict" (or it's modern cousin, "use common::sense", it
871	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1058	is definitely recommended to keep it off in production. Keeping
		1059	"PERL_ANYEVENT_STRICT=1" in your environment while developing
872	while developing programs can be very useful, however.	1060	programs can be very useful, however.
873		1061
874	"PERL_ANYEVENT_MODEL"	1062	"PERL_ANYEVENT_MODEL"
875	This can be used to specify the event model to be used by AnyEvent,	1063	This can be used to specify the event model to be used by AnyEvent,
876	before auto detection and -probing kicks in. It must be a string	1064	before auto detection and -probing kicks in. It must be a string
877	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1065	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
918	EDNS0 in its DNS requests.	1106	EDNS0 in its DNS requests.
919		1107
920	"PERL_ANYEVENT_MAX_FORKS"	1108	"PERL_ANYEVENT_MAX_FORKS"
921	The maximum number of child processes that	1109	The maximum number of child processes that
922	"AnyEvent::Util::fork_call" will create in parallel.	1110	"AnyEvent::Util::fork_call" will create in parallel.
		1111
		1112	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1113	The default value for the "max_outstanding" parameter for the
		1114	default DNS resolver - this is the maximum number of parallel DNS
		1115	requests that are sent to the DNS server.
		1116
		1117	"PERL_ANYEVENT_RESOLV_CONF"
		1118	The file to use instead of /etc/resolv.conf (or OS-specific
		1119	configuration) in the default resolver. When set to the empty
		1120	string, no default config will be used.
		1121
		1122	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1123	When neither "ca_file" nor "ca_path" was specified during
		1124	AnyEvent::TLS context creation, and either of these environment
		1125	variables exist, they will be used to specify CA certificate
		1126	locations instead of a system-dependent default.
		1127
		1128	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1129	When these are set to 1, then the respective modules are not loaded.
		1130	Mostly good for testing AnyEvent itself.
923		1131
924	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1132	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
925	This is an advanced topic that you do not normally need to use AnyEvent	1133	This is an advanced topic that you do not normally need to use AnyEvent
926	in a module. This section is only of use to event loop authors who want	1134	in a module. This section is only of use to event loop authors who want
927	to provide AnyEvent compatibility.	1135	to provide AnyEvent compatibility.
…		…
1163	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1371	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1164	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1372	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1165	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1373	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1166	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1374	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1167	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1375	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1376	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1377	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1168	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1378	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1169	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1379	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1170	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1380	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1171	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1381	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1172		1382
…		…
1201	few of them active), of course, but this was not subject of this	1411	few of them active), of course, but this was not subject of this
1202	benchmark.	1412	benchmark.
1203		1413
1204	The "Event" module has a relatively high setup and callback invocation	1414	The "Event" module has a relatively high setup and callback invocation
1205	cost, but overall scores in on the third place.	1415	cost, but overall scores in on the third place.
		1416
		1417	"IO::Async" performs admirably well, about on par with "Event", even
		1418	when using its pure perl backend.
1206		1419
1207	"Glib"'s memory usage is quite a bit higher, but it features a faster	1420	"Glib"'s memory usage is quite a bit higher, but it features a faster
1208	callback invocation and overall ends up in the same class as "Event".	1421	callback invocation and overall ends up in the same class as "Event".
1209	However, Glib scales extremely badly, doubling the number of watchers	1422	However, Glib scales extremely badly, doubling the number of watchers
1210	increases the processing time by more than a factor of four, making it	1423	increases the processing time by more than a factor of four, making it
…		…
1281	single "request", that is, reading the token from the pipe and	1494	single "request", that is, reading the token from the pipe and
1282	forwarding it to another server. This includes deleting the old timeout	1495	forwarding it to another server. This includes deleting the old timeout
1283	and creating a new one that moves the timeout into the future.	1496	and creating a new one that moves the timeout into the future.
1284		1497
1285	Results	1498	Results
1286	name sockets create request	1499	name sockets create request
1287	EV 20000 69.01 11.16	1500	EV 20000 69.01 11.16
1288	Perl 20000 73.32 35.87	1501	Perl 20000 73.32 35.87
		1502	IOAsync 20000 157.00 98.14 epoll
		1503	IOAsync 20000 159.31 616.06 poll
1289	Event 20000 212.62 257.32	1504	Event 20000 212.62 257.32
1290	Glib 20000 651.16 1896.30	1505	Glib 20000 651.16 1896.30
1291	POE 20000 349.67 12317.24 uses POE::Loop::Event	1506	POE 20000 349.67 12317.24 uses POE::Loop::Event
1292		1507
1293	Discussion	1508	Discussion
1294	This benchmark does measure scalability and overall performance of the	1509	This benchmark does measure scalability and overall performance of the
1295	particular event loop.	1510	particular event loop.
1296		1511
1297	EV is again fastest. Since it is using epoll on my system, the setup	1512	EV is again fastest. Since it is using epoll on my system, the setup
1298	time is relatively high, though.	1513	time is relatively high, though.
1299		1514
1300	Perl surprisingly comes second. It is much faster than the C-based event	1515	Perl surprisingly comes second. It is much faster than the C-based event
1301	loops Event and Glib.	1516	loops Event and Glib.
		1517
		1518	IO::Async performs very well when using its epoll backend, and still
		1519	quite good compared to Glib when using its pure perl backend.
1302		1520
1303	Event suffers from high setup time as well (look at its code and you	1521	Event suffers from high setup time as well (look at its code and you
1304	will understand why). Callback invocation also has a high overhead	1522	will understand why). Callback invocation also has a high overhead
1305	compared to the "$_->() for .."-style loop that the Perl event loop	1523	compared to the "$_->() for .."-style loop that the Perl event loop
1306	uses. Event uses select or poll in basically all documented	1524	uses. Event uses select or poll in basically all documented
…		…
1357		1575
1358	Summary	1576	Summary
1359	* C-based event loops perform very well with small number of watchers,	1577	* C-based event loops perform very well with small number of watchers,
1360	as the management overhead dominates.	1578	as the management overhead dominates.
1361		1579
		1580	THE IO::Lambda BENCHMARK
		1581	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1582	could be misinterpreted to make AnyEvent look bad. In fact, the
		1583	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1584	better (which shouldn't come as a surprise to anybody). As such, the
		1585	benchmark is fine, and mostly shows that the AnyEvent backend from
		1586	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1587	without the extra baggage? To explore this, I wrote the equivalent
		1588	benchmark for AnyEvent.
		1589
		1590	The benchmark itself creates an echo-server, and then, for 500 times,
		1591	connects to the echo server, sends a line, waits for the reply, and then
		1592	creates the next connection. This is a rather bad benchmark, as it
		1593	doesn't test the efficiency of the framework or much non-blocking I/O,
		1594	but it is a benchmark nevertheless.
		1595
		1596	name runtime
		1597	Lambda/select 0.330 sec
		1598	+ optimized 0.122 sec
		1599	Lambda/AnyEvent 0.327 sec
		1600	+ optimized 0.138 sec
		1601	Raw sockets/select 0.077 sec
		1602	POE/select, components 0.662 sec
		1603	POE/select, raw sockets 0.226 sec
		1604	POE/select, optimized 0.404 sec
		1605
		1606	AnyEvent/select/nb 0.085 sec
		1607	AnyEvent/EV/nb 0.068 sec
		1608	+state machine 0.134 sec
		1609
		1610	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1611	benchmarks actually make blocking connects and use 100% blocking I/O,
		1612	defeating the purpose of an event-based solution. All of the newly
		1613	written AnyEvent benchmarks use 100% non-blocking connects (using
		1614	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1615	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1616	connects generally require a lot more bookkeeping and event handling
		1617	than blocking connects (which involve a single syscall only).
		1618
		1619	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1620	offers similar expressive power as POE and IO::Lambda, using
		1621	conventional Perl syntax. This means that both the echo server and the
		1622	client are 100% non-blocking, further placing it at a disadvantage.
		1623
		1624	As you can see, the AnyEvent + EV combination even beats the
		1625	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1626	backend easily beats IO::Lambda and POE.
		1627
		1628	And even the 100% non-blocking version written using the high-level (and
		1629	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a
		1630	large margin, even though it does all of DNS, tcp-connect and socket I/O
		1631	in a non-blocking way.
		1632
		1633	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1634	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1635	part of the IO::lambda distribution and were used without any changes.
		1636
1362	SIGNALS	1637	SIGNALS
1363	AnyEvent currently installs handlers for these signals:	1638	AnyEvent currently installs handlers for these signals:
1364		1639
1365	SIGCHLD	1640	SIGCHLD
1366	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1641	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1367	emulation for event loops that do not support them natively. Also,	1642	emulation for event loops that do not support them natively. Also,
1368	some event loops install a similar handler.	1643	some event loops install a similar handler.
		1644
		1645	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1646	then AnyEvent will reset it to default, to avoid losing child exit
		1647	statuses.
1369		1648
1370	SIGPIPE	1649	SIGPIPE
1371	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1650	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1372	"undef" when AnyEvent gets loaded.	1651	"undef" when AnyEvent gets loaded.
1373		1652
…		…
1381	it is that this way, the handler will be restored to defaults on	1660	it is that this way, the handler will be restored to defaults on
1382	exec.	1661	exec.
1383		1662
1384	Feel free to install your own handler, or reset it to defaults.	1663	Feel free to install your own handler, or reset it to defaults.
1385		1664
		1665	RECOMMENDED/OPTIONAL MODULES
		1666	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1667	it's built-in modules) are required to use it.
		1668
		1669	That does not mean that AnyEvent won't take advantage of some additional
		1670	modules if they are installed.
		1671
		1672	This section epxlains which additional modules will be used, and how
		1673	they affect AnyEvent's operetion.
		1674
		1675	Async::Interrupt
		1676	This slightly arcane module is used to implement fast signal
		1677	handling: To my knowledge, there is no way to do completely
		1678	race-free and quick signal handling in pure perl. To ensure that
		1679	signals still get delivered, AnyEvent will start an interval timer
		1680	to wake up perl (and catch the signals) with some delay (default is
		1681	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1682
		1683	If this module is available, then it will be used to implement
		1684	signal catching, which means that signals will not be delayed, and
		1685	the event loop will not be interrupted regularly, which is more
		1686	efficient (And good for battery life on laptops).
		1687
		1688	This affects not just the pure-perl event loop, but also other event
		1689	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1690
		1691	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1692	natively, and either employ their own workarounds (POE) or use
		1693	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1694	Installing Async::Interrupt does nothing for those backends.
		1695
		1696	EV This module isn't really "optional", as it is simply one of the
		1697	backend event loops that AnyEvent can use. However, it is simply the
		1698	best event loop available in terms of features, speed and stability:
		1699	It supports the AnyEvent API optimally, implements all the watcher
		1700	types in XS, does automatic timer adjustments even when no monotonic
		1701	clock is available, can take avdantage of advanced kernel interfaces
		1702	such as "epoll" and "kqueue", and is the fastest backend by far.
		1703	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1704	Glib::EV).
		1705
		1706	Guard
		1707	The guard module, when used, will be used to implement
		1708	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1709	uses a lot less memory), but otherwise doesn't affect guard
		1710	operation much. It is purely used for performance.
		1711
		1712	JSON and JSON::XS
		1713	This module is required when you want to read or write JSON data via
		1714	AnyEvent::Handle. It is also written in pure-perl, but can take
		1715	advantage of the ultra-high-speed JSON::XS module when it is
		1716	installed.
		1717
		1718	In fact, AnyEvent::Handle will use JSON::XS by default if it is
		1719	installed.
		1720
		1721	Net::SSLeay
		1722	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1723	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1724	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1725
		1726	Time::HiRes
		1727	This module is part of perl since release 5.008. It will be used
		1728	when the chosen event library does not come with a timing source on
		1729	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1730	additionally use it to try to use a monotonic clock for timing
		1731	stability.
		1732
1386	FORK	1733	FORK
1387	Most event libraries are not fork-safe. The ones who are usually are	1734	Most event libraries are not fork-safe. The ones who are usually are
1388	because they rely on inefficient but fork-safe "select" or "poll" calls.	1735	because they rely on inefficient but fork-safe "select" or "poll" calls.
1389	Only EV is fully fork-aware.	1736	Only EV is fully fork-aware.
1390		1737
1391	If you have to fork, you must either do so before creating your first	1738	If you have to fork, you must either do so before creating your first
1392	watcher OR you must not use AnyEvent at all in the child.	1739	watcher OR you must not use AnyEvent at all in the child OR you must do
		1740	something completely out of the scope of AnyEvent.
1393		1741
1394	SECURITY CONSIDERATIONS	1742	SECURITY CONSIDERATIONS
1395	AnyEvent can be forced to load any event model via	1743	AnyEvent can be forced to load any event model via
1396	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1744	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1397	to execute arbitrary code or directly gain access, it can easily be used	1745	to execute arbitrary code or directly gain access, it can easily be used
…		…
1401		1749
1402	You can make AnyEvent completely ignore this variable by deleting it	1750	You can make AnyEvent completely ignore this variable by deleting it
1403	before the first watcher gets created, e.g. with a "BEGIN" block:	1751	before the first watcher gets created, e.g. with a "BEGIN" block:
1404		1752
1405	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1753	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1406		1754
1407	use AnyEvent;	1755	use AnyEvent;
1408		1756
1409	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1757	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1410	be used to probe what backend is used and gain other information (which	1758	be used to probe what backend is used and gain other information (which
1411	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),	1759	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1412	and $ENV{PERL_ANYEGENT_STRICT}.	1760	and $ENV{PERL_ANYEVENT_STRICT}.
		1761
		1762	Note that AnyEvent will remove all environment variables starting with
		1763	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1764	enabled.
1413		1765
1414	BUGS	1766	BUGS
1415	Perl 5.8 has numerous memleaks that sometimes hit this module and are	1767	Perl 5.8 has numerous memleaks that sometimes hit this module and are
1416	hard to work around. If you suffer from memleaks, first upgrade to Perl	1768	hard to work around. If you suffer from memleaks, first upgrade to Perl
1417	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	1769	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
…		…
1424	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1776	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1425	Event::Lib, Qt, POE.	1777	Event::Lib, Qt, POE.
1426		1778
1427	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1779	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1428	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1780	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1429	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1781	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1782	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1430		1783
1431	Non-blocking file handles, sockets, TCP clients and servers:	1784	Non-blocking file handles, sockets, TCP clients and servers:
1432	AnyEvent::Handle, AnyEvent::Socket.	1785	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1433		1786
1434	Asynchronous DNS: AnyEvent::DNS.	1787	Asynchronous DNS: AnyEvent::DNS.
1435		1788
1436	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1789	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1437		1790
1438	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1791	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1792	AnyEvent::HTTP.
1439		1793
1440	AUTHOR	1794	AUTHOR
1441	Marc Lehmann <schmorp@schmorp.de>	1795	Marc Lehmann <schmorp@schmorp.de>
1442	http://home.schmorp.de/	1796	http://home.schmorp.de/
1443		1797

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Comparing AnyEvent/README (file contents): Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs. Revision 1.48 by root, Sun Jul 26 00:17:24 2009 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs.
Revision 1.48 by root, Sun Jul 26 00:17:24 2009 UTC