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Revision 1.11 by root, Sun Jul 15 03:24:18 2001 UTC vs.
Revision 1.297 by root, Thu May 12 23:55:39 2011 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - coroutine process abstraction	3	Coro - the only real threads in perl
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use Coro;	7	use Coro;
8		8
9	async {	9	async {
10	# some asynchronous thread of execution	10	# some asynchronous thread of execution
		11	print "2\n";
		12	cede; # yield back to main
		13	print "4\n";
11	};	14	};
12		15	print "1\n";
13	# alternatively create an async process like this:	16	cede; # yield to coro
14		17	print "3\n";
15	sub some_func : Coro {	18	cede; # and again
16	# some more async code	19
17	}	20	# use locking
18		21	use Coro::Semaphore;
19	yield;	22	my $lock = new Coro::Semaphore;
		23	my $locked;
		24
		25	$lock->down;
		26	$locked = 1;
		27	$lock->up;
20		28
21	=head1 DESCRIPTION	29	=head1 DESCRIPTION
22		30
		31	For a tutorial-style introduction, please read the L<Coro::Intro>
		32	manpage. This manpage mainly contains reference information.
		33
		34	This module collection manages continuations in general, most often in
		35	the form of cooperative threads (also called coros, or simply "coro"
		36	in the documentation). They are similar to kernel threads but don't (in
		37	general) run in parallel at the same time even on SMP machines. The
		38	specific flavor of thread offered by this module also guarantees you that
		39	it will not switch between threads unless necessary, at easily-identified
		40	points in your program, so locking and parallel access are rarely an
		41	issue, making thread programming much safer and easier than using other
		42	thread models.
		43
		44	Unlike the so-called "Perl threads" (which are not actually real threads
		45	but only the windows process emulation (see section of same name for
		46	more details) ported to UNIX, and as such act as processes), Coro
		47	provides a full shared address space, which makes communication between
		48	threads very easy. And coro threads are fast, too: disabling the Windows
		49	process emulation code in your perl and using Coro can easily result in
		50	a two to four times speed increase for your programs. A parallel matrix
		51	multiplication benchmark (very communication-intensive) runs over 300
		52	times faster on a single core than perls pseudo-threads on a quad core
		53	using all four cores.
		54
		55	Coro achieves that by supporting multiple running interpreters that share
		56	data, which is especially useful to code pseudo-parallel processes and
		57	for event-based programming, such as multiple HTTP-GET requests running
		58	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		59	into an event-based environment.
		60
		61	In this module, a thread is defined as "callchain + lexical variables +
		62	some package variables + C stack), that is, a thread has its own callchain,
		63	its own set of lexicals and its own set of perls most important global
		64	variables (see L<Coro::State> for more configuration and background info).
		65
		66	See also the C<SEE ALSO> section at the end of this document - the Coro
		67	module family is quite large.
		68
		69	=head1 CORO THREAD LIFE CYCLE
		70
		71	During the long and exciting (or not) life of a coro thread, it goes
		72	through a number of states:
		73
		74	=over 4
		75
		76	=item 1. Creation
		77
		78	The first thing in the life of a coro thread is it's creation -
		79	obviously. The typical way to create a thread is to call the C<async
		80	BLOCK> function:
		81
		82	async {
		83	# thread code goes here
		84	};
		85
		86	You can also pass arguments, which are put in C<@_>:
		87
		88	async {
		89	print $_[1]; # prints 2
		90	} 1, 2, 3;
		91
		92	This creates a new coro thread and puts it into the ready queue, meaning
		93	it will run as soon as the CPU is free for it.
		94
		95	C<async> will return a Coro object - you can store this for future
		96	reference or ignore it - a thread that is running, ready to run or waiting
		97	for some event is alive on it's own.
		98
		99	Another way to create a thread is to call the C<new> constructor with a
		100	code-reference:
		101
		102	new Coro sub {
		103	# thread code goes here
		104	}, @optional_arguments;
		105
		106	This is quite similar to calling C<async>, but the important difference is
		107	that the new thread is not put into the ready queue, so the thread will
		108	not run until somebody puts it there. C<async> is, therefore, identical to
		109	this sequence:
		110
		111	my $coro = new Coro sub {
		112	# thread code goes here
		113	};
		114	$coro->ready;
		115	return $coro;
		116
		117	=item 2. Startup
		118
		119	When a new coro thread is created, only a copy of the code reference
		120	and the arguments are stored, no extra memory for stacks and so on is
		121	allocated, keeping the coro thread in a low-memory state.
		122
		123	Only when it actually starts executing will all the resources be finally
		124	allocated.
		125
		126	The optional arguments specified at coro creation are available in C<@_>,
		127	similar to function calls.
		128
		129	=item 3. Running / Blocking
		130
		131	A lot can happen after the coro thread has started running. Quite usually,
		132	it will not run to the end in one go (because you could use a function
		133	instead), but it will give up the CPU regularly because it waits for
		134	external events.
		135
		136	As long as a coro thread runs, its Coro object is available in the global
		137	variable C<$Coro::current>.
		138
		139	The low-level way to give up the CPU is to call the scheduler, which
		140	selects a new coro thread to run:
		141
		142	Coro::schedule;
		143
		144	Since running threads are not in the ready queue, calling the scheduler
		145	without doing anything else will block the coro thread forever - you need
		146	to arrange either for the coro to put woken up (readied) by some other
		147	event or some other thread, or you can put it into the ready queue before
		148	scheduling:
		149
		150	# this is exactly what Coro::cede does
		151	$Coro::current->ready;
		152	Coro::schedule;
		153
		154	All the higher-level synchronisation methods (Coro::Semaphore,
		155	Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<<
		156	Coro::schedule >>.
		157
		158	While the coro thread is running it also might get assigned a C-level
		159	thread, or the C-level thread might be unassigned from it, as the Coro
		160	runtime wishes. A C-level thread needs to be assigned when your perl
		161	thread calls into some C-level function and that function in turn calls
		162	perl and perl then wants to switch coroutines. This happens most often
		163	when you run an event loop and block in the callback, or when perl
		164	itself calls some function such as C<AUTOLOAD> or methods via the C<tie>
		165	mechanism.
		166
		167	=item 4. Termination
		168
		169	Many threads actually terminate after some time. There are a number of
		170	ways to terminate a coro thread, the simplest is returning from the
		171	top-level code reference:
		172
		173	async {
		174	# after returning from here, the coro thread is terminated
		175	};
		176
		177	async {
		178	return if 0.5 < rand; # terminate a little earlier, maybe
		179	print "got a chance to print this\n";
		180	# or here
		181	};
		182
		183	Any values returned from the coroutine can be recovered using C<< ->join
		184	>>:
		185
		186	my $coro = async {
		187	"hello, world\n" # return a string
		188	};
		189
		190	my $hello_world = $coro->join;
		191
		192	print $hello_world;
		193
		194	Another way to terminate is to call C<< Coro::terminate >>, which at any
		195	subroutine call nesting level:
		196
		197	async {
		198	Coro::terminate "return value 1", "return value 2";
		199	};
		200
		201	And yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the
		202	coro thread from another thread:
		203
		204	my $coro = async {
		205	exit 1;
		206	};
		207
		208	$coro->cancel; # also accepts values for ->join to retrieve
		209
		210	Cancellation I<can> be dangerous - it's a bit like calling C<exit> without
		211	actually exiting, and might leave C libraries and XS modules in a weird
		212	state. Unlike other thread implementations, however, Coro is exceptionally
		213	safe with regards to cancellation, as perl will always be in a consistent
		214	state, and for those cases where you want to do truly marvellous things
		215	with your coro while it is being cancelled - that is, make sure all
		216	cleanup code is executed from the thread being cancelled - there is even a
		217	C<< ->safe_cancel >> method.
		218
		219	So, cancelling a thread that runs in an XS event loop might not be the
		220	best idea, but any other combination that deals with perl only (cancelling
		221	when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is
		222	safe.
		223
		224	Lastly, a coro thread object that isn't referenced is C<< ->cancel >>'ed
		225	automatically - just like other objects in Perl. This is not such a common
		226	case, however - a running thread is referencedy b C<$Coro::current>, a
		227	thread ready to run is referenced by the ready queue, a thread waiting
		228	on a lock or semaphore is referenced by being in some wait list and so
		229	on. But a thread that isn't in any of those queues gets cancelled:
		230
		231	async {
		232	schedule; # cede to other coros, don't go into the ready queue
		233	};
		234
		235	cede;
		236	# now the async above is destroyed, as it is not referenced by anything.
		237
		238	=item 5. Cleanup
		239
		240	Threads will allocate various resources. Most but not all will be returned
		241	when a thread terminates, during clean-up.
		242
		243	Cleanup is quite similar to throwing an uncaught exception: perl will
		244	work it's way up through all subroutine calls and blocks. On it's way, it
		245	will release all C<my> variables, undo all C<local>'s and free any other
		246	resources truly local to the thread.
		247
		248	So, a common way to free resources is to keep them referenced only by my
		249	variables:
		250
		251	async {
		252	my $big_cache = new Cache ...;
		253	};
		254
		255	If there are no other references, then the C<$big_cache> object will be
		256	freed when the thread terminates, regardless of how it does so.
		257
		258	What it does C<NOT> do is unlock any Coro::Semaphores or similar
		259	resources, but that's where the C<guard> methods come in handy:
		260
		261	my $sem = new Coro::Semaphore;
		262
		263	async {
		264	my $lock_guard = $sem->guard;
		265	# if we reutrn, or die or get cancelled, here,
		266	# then the semaphore will be "up"ed.
		267	};
		268
		269	The C<Guard::guard> function comes in handy for any custom cleanup you
		270	might want to do (but you cannot switch to other coroutines form those
		271	code blocks):
		272
		273	async {
		274	my $window = new Gtk2::Window "toplevel";
		275	# The window will not be cleaned up automatically, even when $window
		276	# gets freed, so use a guard to ensure it's destruction
		277	# in case of an error:
		278	my $window_guard = Guard::guard { $window->destroy };
		279
		280	# we are safe here
		281	};
		282
		283	Last not least, C<local> can often be handy, too, e.g. when temporarily
		284	replacing the coro thread description:
		285
		286	sub myfunction {
		287	local $Coro::current->{desc} = "inside myfunction(@_)";
		288
		289	# if we return or die here, the description will be restored
		290	}
		291
		292	=item 6. Viva La Zombie Muerte
		293
		294	Even after a thread has terminated and cleaned up its resources, the Coro
		295	object still is there and stores the return values of the thread.
		296
		297	The means the Coro object gets freed automatically when the thread has
		298	terminated and cleaned up and there arenot other references.
		299
		300	If there are, the Coro object will stay around, and you can call C<<
		301	->join >> as many times as you wish to retrieve the result values:
		302
		303	async {
		304	print "hi\n";
		305	1
		306	};
		307
		308	# run the async above, and free everything before returning
		309	# from Coro::cede:
		310	Coro::cede;
		311
		312	{
		313	my $coro = async {
		314	print "hi\n";
		315	1
		316	};
		317
		318	# run the async above, and clean up, but do not free the coro
		319	# object:
		320	Coro::cede;
		321
		322	# optionally retrieve the result values
		323	my @results = $coro->join;
		324
		325	# now $coro goes out of scope, and presumably gets freed
		326	};
		327
		328	=back
		329
23	=cut	330	=cut
24		331
25	package Coro;	332	package Coro;
26		333
		334	use common::sense;
		335
		336	use Carp ();
		337
		338	use Guard ();
		339
27	use Coro::State;	340	use Coro::State;
28		341
29	use base Exporter;	342	use base qw(Coro::State Exporter);
30		343
31	$VERSION = 0.04;	344	our $idle; # idle handler
		345	our $main; # main coro
		346	our $current; # current coro
32		347
33	@EXPORT = qw(async yield schedule);	348	our $VERSION = 5.372;
34	@EXPORT_OK = qw($current);
35		349
36	{	350	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
37	use subs 'async';	351	our %EXPORT_TAGS = (
		352	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		353	);
		354	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
38		355
39	my @async;	356	=head1 GLOBAL VARIABLES
40		357
41	# this way of handling attributes simply is NOT scalable ;()	358	=over 4
42	sub import {	359
43	Coro->export_to_level(1, @_);	360	=item $Coro::main
44	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};	361
45	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {	362	This variable stores the Coro object that represents the main
46	my ($package, $ref) = (shift, shift);	363	program. While you cna C<ready> it and do most other things you can do to
47	my @attrs;	364	coro, it is mainly useful to compare again C<$Coro::current>, to see
48	for (@_) {	365	whether you are running in the main program or not.
49	if ($_ eq "Coro") {	366
50	push @async, $ref;	367	=cut
51	} else {	368
52	push @attrs, @_;	369	# $main is now being initialised by Coro::State
53	}	370
54	}	371	=item $Coro::current
55	return $old ? $old->($package, $name, @attrs) : @attrs;	372
		373	The Coro object representing the current coro (the last
		374	coro that the Coro scheduler switched to). The initial value is
		375	C<$Coro::main> (of course).
		376
		377	This variable is B<strictly> I<read-only>. You can take copies of the
		378	value stored in it and use it as any other Coro object, but you must
		379	not otherwise modify the variable itself.
		380
		381	=cut
		382
		383	sub current() { $current } # [DEPRECATED]
		384
		385	=item $Coro::idle
		386
		387	This variable is mainly useful to integrate Coro into event loops. It is
		388	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		389	pretty low-level functionality.
		390
		391	This variable stores a Coro object that is put into the ready queue when
		392	there are no other ready threads (without invoking any ready hooks).
		393
		394	The default implementation dies with "FATAL: deadlock detected.", followed
		395	by a thread listing, because the program has no other way to continue.
		396
		397	This hook is overwritten by modules such as C<Coro::EV> and
		398	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
		399	coro so the scheduler can run it.
		400
		401	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
		402
		403	=cut
		404
		405	# ||= because other modules could have provided their own by now
		406	$idle ||= new Coro sub {
		407	require Coro::Debug;
		408	die "FATAL: deadlock detected.\n"
		409	. Coro::Debug::ps_listing ();
		410	};
		411
		412	# this coro is necessary because a coro
		413	# cannot destroy itself.
		414	our @destroy;
		415	our $manager;
		416
		417	$manager = new Coro sub {
		418	while () {
		419	_destroy shift @destroy
		420	while @destroy;
		421
		422	&schedule;
		423	}
		424	};
		425	$manager->{desc} = "[coro manager]";
		426	$manager->prio (PRIO_MAX);
		427
		428	=back
		429
		430	=head1 SIMPLE CORO CREATION
		431
		432	=over 4
		433
		434	=item async { ... } [@args...]
		435
		436	Create a new coro and return its Coro object (usually
		437	unused). The coro will be put into the ready queue, so
		438	it will start running automatically on the next scheduler run.
		439
		440	The first argument is a codeblock/closure that should be executed in the
		441	coro. When it returns argument returns the coro is automatically
		442	terminated.
		443
		444	The remaining arguments are passed as arguments to the closure.
		445
		446	See the C<Coro::State::new> constructor for info about the coro
		447	environment in which coro are executed.
		448
		449	Calling C<exit> in a coro will do the same as calling exit outside
		450	the coro. Likewise, when the coro dies, the program will exit,
		451	just as it would in the main program.
		452
		453	If you do not want that, you can provide a default C<die> handler, or
		454	simply avoid dieing (by use of C<eval>).
		455
		456	Example: Create a new coro that just prints its arguments.
		457
		458	async {
		459	print "@_\n";
		460	} 1,2,3,4;
		461
		462	=item async_pool { ... } [@args...]
		463
		464	Similar to C<async>, but uses a coro pool, so you should not call
		465	terminate or join on it (although you are allowed to), and you get a
		466	coro that might have executed other code already (which can be good
		467	or bad :).
		468
		469	On the plus side, this function is about twice as fast as creating (and
		470	destroying) a completely new coro, so if you need a lot of generic
		471	coros in quick successsion, use C<async_pool>, not C<async>.
		472
		473	The code block is executed in an C<eval> context and a warning will be
		474	issued in case of an exception instead of terminating the program, as
		475	C<async> does. As the coro is being reused, stuff like C<on_destroy>
		476	will not work in the expected way, unless you call terminate or cancel,
		477	which somehow defeats the purpose of pooling (but is fine in the
		478	exceptional case).
		479
		480	The priority will be reset to C<0> after each run, tracing will be
		481	disabled, the description will be reset and the default output filehandle
		482	gets restored, so you can change all these. Otherwise the coro will
		483	be re-used "as-is": most notably if you change other per-coro global
		484	stuff such as C<$/> you I<must needs> revert that change, which is most
		485	simply done by using local as in: C<< local $/ >>.
		486
		487	The idle pool size is limited to C<8> idle coros (this can be
		488	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		489	coros as required.
		490
		491	If you are concerned about pooled coros growing a lot because a
		492	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		493	{ terminate }> once per second or so to slowly replenish the pool. In
		494	addition to that, when the stacks used by a handler grows larger than 32kb
		495	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		496
		497	=cut
		498
		499	our $POOL_SIZE = 8;
		500	our $POOL_RSS = 32 * 1024;
		501	our @async_pool;
		502
		503	sub pool_handler {
		504	while () {
		505	eval {
		506	&{&_pool_handler} while 1;
56	};	507	};
57	}
58		508
59	sub INIT {	509	warn $@ if $@;
60	async pop @async while @async;
61	}	510	}
62	}	511	}
63		512
64	=item $main	513	=back
65		514
66	This coroutine represents the main program.	515	=head1 STATIC METHODS
		516
		517	Static methods are actually functions that implicitly operate on the
		518	current coro.
		519
		520	=over 4
		521
		522	=item schedule
		523
		524	Calls the scheduler. The scheduler will find the next coro that is
		525	to be run from the ready queue and switches to it. The next coro
		526	to be run is simply the one with the highest priority that is longest
		527	in its ready queue. If there is no coro ready, it will call the
		528	C<$Coro::idle> hook.
		529
		530	Please note that the current coro will I<not> be put into the ready
		531	queue, so calling this function usually means you will never be called
		532	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		533	thus waking you up.
		534
		535	This makes C<schedule> I<the> generic method to use to block the current
		536	coro and wait for events: first you remember the current coro in
		537	a variable, then arrange for some callback of yours to call C<< ->ready
		538	>> on that once some event happens, and last you call C<schedule> to put
		539	yourself to sleep. Note that a lot of things can wake your coro up,
		540	so you need to check whether the event indeed happened, e.g. by storing the
		541	status in a variable.
		542
		543	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
		544
		545	=item cede
		546
		547	"Cede" to other coros. This function puts the current coro into
		548	the ready queue and calls C<schedule>, which has the effect of giving
		549	up the current "timeslice" to other coros of the same or higher
		550	priority. Once your coro gets its turn again it will automatically be
		551	resumed.
		552
		553	This function is often called C<yield> in other languages.
		554
		555	=item Coro::cede_notself
		556
		557	Works like cede, but is not exported by default and will cede to I<any>
		558	coro, regardless of priority. This is useful sometimes to ensure
		559	progress is made.
		560
		561	=item terminate [arg...]
		562
		563	Terminates the current coro with the given status values (see
		564	L<cancel>). The values will not be copied, but referenced directly.
		565
		566	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		567
		568	These function install enter and leave winders in the current scope. The
		569	enter block will be executed when on_enter is called and whenever the
		570	current coro is re-entered by the scheduler, while the leave block is
		571	executed whenever the current coro is blocked by the scheduler, and
		572	also when the containing scope is exited (by whatever means, be it exit,
		573	die, last etc.).
		574
		575	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		576	BLOCKs>. That means: do not even think about calling C<die> without an
		577	eval, and do not even think of entering the scheduler in any way.
		578
		579	Since both BLOCKs are tied to the current scope, they will automatically
		580	be removed when the current scope exits.
		581
		582	These functions implement the same concept as C<dynamic-wind> in scheme
		583	does, and are useful when you want to localise some resource to a specific
		584	coro.
		585
		586	They slow down thread switching considerably for coros that use them
		587	(about 40% for a BLOCK with a single assignment, so thread switching is
		588	still reasonably fast if the handlers are fast).
		589
		590	These functions are best understood by an example: The following function
		591	will change the current timezone to "Antarctica/South_Pole", which
		592	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		593	which remember/change the current timezone and restore the previous
		594	value, respectively, the timezone is only changed for the coro that
		595	installed those handlers.
		596
		597	use POSIX qw(tzset);
		598
		599	async {
		600	my $old_tz; # store outside TZ value here
		601
		602	Coro::on_enter {
		603	$old_tz = $ENV{TZ}; # remember the old value
		604
		605	$ENV{TZ} = "Antarctica/South_Pole";
		606	tzset; # enable new value
		607	};
		608
		609	Coro::on_leave {
		610	$ENV{TZ} = $old_tz;
		611	tzset; # restore old value
		612	};
		613
		614	# at this place, the timezone is Antarctica/South_Pole,
		615	# without disturbing the TZ of any other coro.
		616	};
		617
		618	This can be used to localise about any resource (locale, uid, current
		619	working directory etc.) to a block, despite the existance of other
		620	coros.
		621
		622	Another interesting example implements time-sliced multitasking using
		623	interval timers (this could obviously be optimised, but does the job):
		624
		625	# "timeslice" the given block
		626	sub timeslice(&) {
		627	use Time::HiRes ();
		628
		629	Coro::on_enter {
		630	# on entering the thread, we set an VTALRM handler to cede
		631	$SIG{VTALRM} = sub { cede };
		632	# and then start the interval timer
		633	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		634	};
		635	Coro::on_leave {
		636	# on leaving the thread, we stop the interval timer again
		637	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		638	};
		639
		640	&{+shift};
		641	}
		642
		643	# use like this:
		644	timeslice {
		645	# The following is an endless loop that would normally
		646	# monopolise the process. Since it runs in a timesliced
		647	# environment, it will regularly cede to other threads.
		648	while () { }
		649	};
		650
		651
		652	=item killall
		653
		654	Kills/terminates/cancels all coros except the currently running one.
		655
		656	Note that while this will try to free some of the main interpreter
		657	resources if the calling coro isn't the main coro, but one
		658	cannot free all of them, so if a coro that is not the main coro
		659	calls this function, there will be some one-time resource leak.
67		660
68	=cut	661	=cut
69		662
70	our $main = new Coro;	663	sub killall {
		664	for (Coro::State::list) {
		665	$_->cancel
		666	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		667	}
		668	}
71		669
72	=item $current	670	=back
73		671
74	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	672	=head1 CORO OBJECT METHODS
		673
		674	These are the methods you can call on coro objects (or to create
		675	them).
		676
		677	=over 4
		678
		679	=item new Coro \&sub [, @args...]
		680
		681	Create a new coro and return it. When the sub returns, the coro
		682	automatically terminates as if C<terminate> with the returned values were
		683	called. To make the coro run you must first put it into the ready
		684	queue by calling the ready method.
		685
		686	See C<async> and C<Coro::State::new> for additional info about the
		687	coro environment.
75		688
76	=cut	689	=cut
77		690
78	# maybe some other module used Coro::Specific before...	691	sub _coro_run {
79	if ($current) {	692	terminate &{+shift};
80	$main->{specific} = $current->{specific};
81	}	693	}
82		694
83	our $current = $main;	695	=item $success = $coro->ready
84		696
85	=item $idle	697	Put the given coro into the end of its ready queue (there is one
		698	queue for each priority) and return true. If the coro is already in
		699	the ready queue, do nothing and return false.
86		700
87	The coroutine to switch to when no other coroutine is running. The default	701	This ensures that the scheduler will resume this coro automatically
88	implementation prints "FATAL: deadlock detected" and exits.	702	once all the coro of higher priority and all coro of the same
		703	priority that were put into the ready queue earlier have been resumed.
		704
		705	=item $coro->suspend
		706
		707	Suspends the specified coro. A suspended coro works just like any other
		708	coro, except that the scheduler will not select a suspended coro for
		709	execution.
		710
		711	Suspending a coro can be useful when you want to keep the coro from
		712	running, but you don't want to destroy it, or when you want to temporarily
		713	freeze a coro (e.g. for debugging) to resume it later.
		714
		715	A scenario for the former would be to suspend all (other) coros after a
		716	fork and keep them alive, so their destructors aren't called, but new
		717	coros can be created.
		718
		719	=item $coro->resume
		720
		721	If the specified coro was suspended, it will be resumed. Note that when
		722	the coro was in the ready queue when it was suspended, it might have been
		723	unreadied by the scheduler, so an activation might have been lost.
		724
		725	To avoid this, it is best to put a suspended coro into the ready queue
		726	unconditionally, as every synchronisation mechanism must protect itself
		727	against spurious wakeups, and the one in the Coro family certainly do
		728	that.
		729
		730	=item $state->is_new
		731
		732	Returns true iff this Coro object is "new", i.e. has never been run
		733	yet. Those states basically consist of only the code reference to call and
		734	the arguments, but consumes very little other resources. New states will
		735	automatically get assigned a perl interpreter when they are transfered to.
		736
		737	=item $state->is_zombie
		738
		739	Returns true iff the Coro object has been cancelled, i.e.
		740	it's resources freed because they were C<cancel>'ed, C<terminate>'d,
		741	C<safe_cancel>'ed or simply went out of scope.
		742
		743	The name "zombie" stems from UNIX culture, where a process that has
		744	exited and only stores and exit status and no other resources is called a
		745	"zombie".
		746
		747	=item $is_ready = $coro->is_ready
		748
		749	Returns true iff the Coro object is in the ready queue. Unless the Coro
		750	object gets destroyed, it will eventually be scheduled by the scheduler.
		751
		752	=item $is_running = $coro->is_running
		753
		754	Returns true iff the Coro object is currently running. Only one Coro object
		755	can ever be in the running state (but it currently is possible to have
		756	multiple running Coro::States).
		757
		758	=item $is_suspended = $coro->is_suspended
		759
		760	Returns true iff this Coro object has been suspended. Suspended Coros will
		761	not ever be scheduled.
		762
		763	=item $coro->cancel (arg...)
		764
		765	Terminates the given Coro thread and makes it return the given arguments as
		766	status (default: an empty list). Never returns if the Coro is the
		767	current Coro.
		768
		769	This is a rather brutal way to free a coro, with some limitations - if
		770	the thread is inside a C callback that doesn't expect to be canceled,
		771	bad things can happen, or if the cancelled thread insists on running
		772	complicated cleanup handlers that rely on it'S thread context, things will
		773	not work.
		774
		775	Any cleanup code being run (e.g. from C<guard> blocks) will be run without
		776	a thread context, and is not allowed to switch to other threads. On the
		777	plus side, C<< ->cancel >> will always clean up the thread, no matter
		778	what. If your cleanup code is complex or you want to avoid cancelling a
		779	C-thread that doesn't know how to clean up itself, it can be better to C<<
		780	->throw >> an exception, or use C<< ->safe_cancel >>.
		781
		782	The arguments to C<< ->cancel >> are not copied, but instead will
		783	be referenced directly (e.g. if you pass C<$var> and after the call
		784	change that variable, then you might change the return values passed to
		785	e.g. C<join>, so don't do that).
		786
		787	The resources of the Coro are usually freed (or destructed) before this
		788	call returns, but this can be delayed for an indefinite amount of time, as
		789	in some cases the manager thread has to run first to actually destruct the
		790	Coro object.
		791
		792	=item $coro->safe_cancel ($arg...)
		793
		794	Works mostly like C<< ->cancel >>, but is inherently "safer", and
		795	consequently, can fail with an exception in cases the thread is not in a
		796	cancellable state.
		797
		798	This method works a bit like throwing an exception that cannot be caught
		799	- specifically, it will clean up the thread from within itself, so
		800	all cleanup handlers (e.g. C<guard> blocks) are run with full thread
		801	context and can block if they wish. The downside is that there is no
		802	guarantee that the thread can be cancelled when you call this method, and
		803	therefore, it might fail. It is also considerably slower than C<cancel> or
		804	C<terminate>.
		805
		806	A thread is in a safe-cancellable state if it either hasn't been run yet,
		807	or it has no C context attached and is inside an SLF function.
		808
		809	The latter two basically mean that the thread isn't currently inside a
		810	perl callback called from some C function (usually via some XS modules)
		811	and isn't currently executing inside some C function itself (via Coro's XS
		812	API).
		813
		814	This call returns true when it could cancel the thread, or croaks with an
		815	error otherwise (i.e. it either returns true or doesn't return at all).
		816
		817	Why the weird interface? Well, there are two common models on how and
		818	when to cancel things. In the first, you have the expectation that your
		819	coro thread can be cancelled when you want to cancel it - if the thread
		820	isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >>
		821	croaks to notify of the bug.
		822
		823	In the second model you sometimes want to ask nicely to cancel a thread,
		824	but if it's not a good time, well, then don't cancel. This can be done
		825	relatively easy like this:
		826
		827	if (! eval { $coro->safe_cancel }) {
		828	warn "unable to cancel thread: $@";
		829	}
		830
		831	However, what you never should do is first try to cancel "safely" and
		832	if that fails, cancel the "hard" way with C<< ->cancel >>. That makes
		833	no sense: either you rely on being able to execute cleanup code in your
		834	thread context, or you don't. If you do, then C<< ->safe_cancel >> is the
		835	only way, and if you don't, then C<< ->cancel >> is always faster and more
		836	direct.
		837
		838	=item $coro->schedule_to
		839
		840	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		841	of continuing with the next coro from the ready queue, always switch to
		842	the given coro object (regardless of priority etc.). The readyness
		843	state of that coro isn't changed.
		844
		845	This is an advanced method for special cases - I'd love to hear about any
		846	uses for this one.
		847
		848	=item $coro->cede_to
		849
		850	Like C<schedule_to>, but puts the current coro into the ready
		851	queue. This has the effect of temporarily switching to the given
		852	coro, and continuing some time later.
		853
		854	This is an advanced method for special cases - I'd love to hear about any
		855	uses for this one.
		856
		857	=item $coro->throw ([$scalar])
		858
		859	If C<$throw> is specified and defined, it will be thrown as an exception
		860	inside the coro at the next convenient point in time. Otherwise
		861	clears the exception object.
		862
		863	Coro will check for the exception each time a schedule-like-function
		864	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		865	>>, C<< Coro::Handle->readable >> and so on. Most of those functions (all
		866	that are part of Coro itself) detect this case and return early in case an
		867	exception is pending.
		868
		869	The exception object will be thrown "as is" with the specified scalar in
		870	C<$@>, i.e. if it is a string, no line number or newline will be appended
		871	(unlike with C<die>).
		872
		873	This can be used as a softer means than either C<cancel> or C<safe_cancel
		874	>to ask a coro to end itself, although there is no guarantee that the
		875	exception will lead to termination, and if the exception isn't caught it
		876	might well end the whole program.
		877
		878	You might also think of C<throw> as being the moral equivalent of
		879	C<kill>ing a coro with a signal (in this case, a scalar).
		880
		881	=item $coro->join
		882
		883	Wait until the coro terminates and return any values given to the
		884	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		885	from multiple threads, and all will be resumed and given the status
		886	return once the C<$coro> terminates.
		887
		888	=item $coro->on_destroy (\&cb)
		889
		890	Registers a callback that is called when this coro thread gets destroyed,
		891	that is, after it's resources have been freed but before it is joined. The
		892	callback gets passed the terminate/cancel arguments, if any, and I<must
		893	not> die, under any circumstances.
		894
		895	There can be any number of C<on_destroy> callbacks per coro, and there is
		896	no way currently to remove a callback once added.
		897
		898	=item $oldprio = $coro->prio ($newprio)
		899
		900	Sets (or gets, if the argument is missing) the priority of the
		901	coro thread. Higher priority coro get run before lower priority
		902	coros. Priorities are small signed integers (currently -4 .. +3),
		903	that you can refer to using PRIO_xxx constants (use the import tag :prio
		904	to get then):
		905
		906	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		907	3 > 1 > 0 > -1 > -3 > -4
		908
		909	# set priority to HIGH
		910	current->prio (PRIO_HIGH);
		911
		912	The idle coro thread ($Coro::idle) always has a lower priority than any
		913	existing coro.
		914
		915	Changing the priority of the current coro will take effect immediately,
		916	but changing the priority of a coro in the ready queue (but not running)
		917	will only take effect after the next schedule (of that coro). This is a
		918	bug that will be fixed in some future version.
		919
		920	=item $newprio = $coro->nice ($change)
		921
		922	Similar to C<prio>, but subtract the given value from the priority (i.e.
		923	higher values mean lower priority, just as in UNIX's nice command).
		924
		925	=item $olddesc = $coro->desc ($newdesc)
		926
		927	Sets (or gets in case the argument is missing) the description for this
		928	coro thread. This is just a free-form string you can associate with a
		929	coro.
		930
		931	This method simply sets the C<< $coro->{desc} >> member to the given
		932	string. You can modify this member directly if you wish, and in fact, this
		933	is often preferred to indicate major processing states that cna then be
		934	seen for example in a L<Coro::Debug> session:
		935
		936	sub my_long_function {
		937	local $Coro::current->{desc} = "now in my_long_function";
		938	...
		939	$Coro::current->{desc} = "my_long_function: phase 1";
		940	...
		941	$Coro::current->{desc} = "my_long_function: phase 2";
		942	...
		943	}
89		944
90	=cut	945	=cut
91		946
92	# should be done using priorities :(	947	sub desc {
		948	my $old = $_[0]{desc};
		949	$_[0]{desc} = $_[1] if @_ > 1;
		950	$old;
		951	}
		952
		953	sub transfer {
		954	require Carp;
		955	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		956	}
		957
		958	=back
		959
		960	=head1 GLOBAL FUNCTIONS
		961
		962	=over 4
		963
		964	=item Coro::nready
		965
		966	Returns the number of coro that are currently in the ready state,
		967	i.e. that can be switched to by calling C<schedule> directory or
		968	indirectly. The value C<0> means that the only runnable coro is the
		969	currently running one, so C<cede> would have no effect, and C<schedule>
		970	would cause a deadlock unless there is an idle handler that wakes up some
		971	coro.
		972
		973	=item my $guard = Coro::guard { ... }
		974
		975	This function still exists, but is deprecated. Please use the
		976	C<Guard::guard> function instead.
		977
		978	=cut
		979
		980	BEGIN { *guard = \&Guard::guard }
		981
		982	=item unblock_sub { ... }
		983
		984	This utility function takes a BLOCK or code reference and "unblocks" it,
		985	returning a new coderef. Unblocking means that calling the new coderef
		986	will return immediately without blocking, returning nothing, while the
		987	original code ref will be called (with parameters) from within another
		988	coro.
		989
		990	The reason this function exists is that many event libraries (such as
		991	the venerable L<Event|Event> module) are not thread-safe (a weaker form
		992	of reentrancy). This means you must not block within event callbacks,
		993	otherwise you might suffer from crashes or worse. The only event library
		994	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		995	you might still run into deadlocks if all event loops are blocked).
		996
		997	Coro will try to catch you when you block in the event loop
		998	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
		999	only works when you do not run your own event loop.
		1000
		1001	This function allows your callbacks to block by executing them in another
		1002	coro where it is safe to block. One example where blocking is handy
		1003	is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
		1004	disk, for example.
		1005
		1006	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		1007	creating event callbacks that want to block.
		1008
		1009	If your handler does not plan to block (e.g. simply sends a message to
		1010	another coro, or puts some other coro into the ready queue), there is
		1011	no reason to use C<unblock_sub>.
		1012
		1013	Note that you also need to use C<unblock_sub> for any other callbacks that
		1014	are indirectly executed by any C-based event loop. For example, when you
		1015	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		1016	provides callbacks that are the result of some event callback, then you
		1017	must not block either, or use C<unblock_sub>.
		1018
		1019	=cut
		1020
		1021	our @unblock_queue;
		1022
		1023	# we create a special coro because we want to cede,
		1024	# to reduce pressure on the coro pool (because most callbacks
		1025	# return immediately and can be reused) and because we cannot cede
		1026	# inside an event callback.
93	our $idle = new Coro sub {	1027	our $unblock_scheduler = new Coro sub {
94	print STDERR "FATAL: deadlock detected\n";	1028	while () {
95	exit(51);	1029	while (my $cb = pop @unblock_queue) {
		1030	&async_pool (@$cb);
		1031
		1032	# for short-lived callbacks, this reduces pressure on the coro pool
		1033	# as the chance is very high that the async_poll coro will be back
		1034	# in the idle state when cede returns
		1035	cede;
		1036	}
		1037	schedule; # sleep well
		1038	}
96	};	1039	};
		1040	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
97		1041
98	# we really need priorities...	1042	sub unblock_sub(&) {
99	my @ready = (); # the ready queue. hehe, rather broken ;)	1043	my $cb = shift;
100		1044
101	# static methods. not really.	1045	sub {
		1046	unshift @unblock_queue, [$cb, @_];
		1047	$unblock_scheduler->ready;
		1048	}
		1049	}
102		1050
103	=head2 STATIC METHODS	1051	=item $cb = rouse_cb
104		1052
105	Static methods are actually functions that operate on the current process only.	1053	Create and return a "rouse callback". That's a code reference that,
		1054	when called, will remember a copy of its arguments and notify the owner
		1055	coro of the callback.
		1056
		1057	See the next function.
		1058
		1059	=item @args = rouse_wait [$cb]
		1060
		1061	Wait for the specified rouse callback (or the last one that was created in
		1062	this coro).
		1063
		1064	As soon as the callback is invoked (or when the callback was invoked
		1065	before C<rouse_wait>), it will return the arguments originally passed to
		1066	the rouse callback. In scalar context, that means you get the I<last>
		1067	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		1068	statement at the end.
		1069
		1070	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		1071
		1072	=back
		1073
		1074	=cut
		1075
		1076	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1077	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1078
		1079	*{"Coro::$module\::new"} = sub {
		1080	require "Coro/$module.pm";
		1081
		1082	# some modules have their new predefined in State.xs, some don't
		1083	*{"Coro::$module\::new"} = $old
		1084	if $old;
		1085
		1086	goto &{"Coro::$module\::new"};
		1087	};
		1088	}
		1089
		1090	1;
		1091
		1092	=head1 HOW TO WAIT FOR A CALLBACK
		1093
		1094	It is very common for a coro to wait for some callback to be
		1095	called. This occurs naturally when you use coro in an otherwise
		1096	event-based program, or when you use event-based libraries.
		1097
		1098	These typically register a callback for some event, and call that callback
		1099	when the event occured. In a coro, however, you typically want to
		1100	just wait for the event, simplyifying things.
		1101
		1102	For example C<< AnyEvent->child >> registers a callback to be called when
		1103	a specific child has exited:
		1104
		1105	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		1106
		1107	But from within a coro, you often just want to write this:
		1108
		1109	my $status = wait_for_child $pid;
		1110
		1111	Coro offers two functions specifically designed to make this easy,
		1112	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		1113
		1114	The first function, C<rouse_cb>, generates and returns a callback that,
		1115	when invoked, will save its arguments and notify the coro that
		1116	created the callback.
		1117
		1118	The second function, C<rouse_wait>, waits for the callback to be called
		1119	(by calling C<schedule> to go to sleep) and returns the arguments
		1120	originally passed to the callback.
		1121
		1122	Using these functions, it becomes easy to write the C<wait_for_child>
		1123	function mentioned above:
		1124
		1125	sub wait_for_child($) {
		1126	my ($pid) = @_;
		1127
		1128	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		1129
		1130	my ($rpid, $rstatus) = Coro::rouse_wait;
		1131	$rstatus
		1132	}
		1133
		1134	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		1135	you can roll your own, using C<schedule>:
		1136
		1137	sub wait_for_child($) {
		1138	my ($pid) = @_;
		1139
		1140	# store the current coro in $current,
		1141	# and provide result variables for the closure passed to ->child
		1142	my $current = $Coro::current;
		1143	my ($done, $rstatus);
		1144
		1145	# pass a closure to ->child
		1146	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		1147	$rstatus = $_[1]; # remember rstatus
		1148	$done = 1; # mark $rstatus as valud
		1149	});
		1150
		1151	# wait until the closure has been called
		1152	schedule while !$done;
		1153
		1154	$rstatus
		1155	}
		1156
		1157
		1158	=head1 BUGS/LIMITATIONS
106		1159
107	=over 4	1160	=over 4
108		1161
109	=item async { ... };	1162	=item fork with pthread backend
110		1163
111	Create a new asynchronous process and return it's process object	1164	When Coro is compiled using the pthread backend (which isn't recommended
112	(usually unused). When the sub returns the new process is automatically	1165	but required on many BSDs as their libcs are completely broken), then
113	terminated.	1166	coro will not survive a fork. There is no known workaround except to
		1167	fix your libc and use a saner backend.
		1168
		1169	=item perl process emulation ("threads")
		1170
		1171	This module is not perl-pseudo-thread-safe. You should only ever use this
		1172	module from the first thread (this requirement might be removed in the
		1173	future to allow per-thread schedulers, but Coro::State does not yet allow
		1174	this). I recommend disabling thread support and using processes, as having
		1175	the windows process emulation enabled under unix roughly halves perl
		1176	performance, even when not used.
		1177
		1178	Attempts to use threads created in another emulated process will crash
		1179	("cleanly", with a null pointer exception).
		1180
		1181	=item coro switching is not signal safe
		1182
		1183	You must not switch to another coro from within a signal handler (only
		1184	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1185	you are sure you are not interrupting a Coro function.
		1186
		1187	That means you I<MUST NOT> call any function that might "block" the
		1188	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		1189	anything that calls those. Everything else, including calling C<ready>,
		1190	works.
		1191
		1192	=back
		1193
		1194
		1195	=head1 WINDOWS PROCESS EMULATION
		1196
		1197	A great many people seem to be confused about ithreads (for example, Chip
		1198	Salzenberg called me unintelligent, incapable, stupid and gullible,
		1199	while in the same mail making rather confused statements about perl
		1200	ithreads (for example, that memory or files would be shared), showing his
		1201	lack of understanding of this area - if it is hard to understand for Chip,
		1202	it is probably not obvious to everybody).
		1203
		1204	What follows is an ultra-condensed version of my talk about threads in
		1205	scripting languages given on the perl workshop 2009:
		1206
		1207	The so-called "ithreads" were originally implemented for two reasons:
		1208	first, to (badly) emulate unix processes on native win32 perls, and
		1209	secondly, to replace the older, real thread model ("5.005-threads").
		1210
		1211	It does that by using threads instead of OS processes. The difference
		1212	between processes and threads is that threads share memory (and other
		1213	state, such as files) between threads within a single process, while
		1214	processes do not share anything (at least not semantically). That
		1215	means that modifications done by one thread are seen by others, while
		1216	modifications by one process are not seen by other processes.
		1217
		1218	The "ithreads" work exactly like that: when creating a new ithreads
		1219	process, all state is copied (memory is copied physically, files and code
		1220	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		1221	the same behaviour can be achieved by using operating system processes,
		1222	except that UNIX typically uses hardware built into the system to do this
		1223	efficiently, while the windows process emulation emulates this hardware in
		1224	software (rather efficiently, but of course it is still much slower than
		1225	dedicated hardware).
		1226
		1227	As mentioned before, loading code, modifying code, modifying data
		1228	structures and so on is only visible in the ithreads process doing the
		1229	modification, not in other ithread processes within the same OS process.
		1230
		1231	This is why "ithreads" do not implement threads for perl at all, only
		1232	processes. What makes it so bad is that on non-windows platforms, you can
		1233	actually take advantage of custom hardware for this purpose (as evidenced
		1234	by the forks module, which gives you the (i-) threads API, just much
		1235	faster).
		1236
		1237	Sharing data is in the i-threads model is done by transfering data
		1238	structures between threads using copying semantics, which is very slow -
		1239	shared data simply does not exist. Benchmarks using i-threads which are
		1240	communication-intensive show extremely bad behaviour with i-threads (in
		1241	fact, so bad that Coro, which cannot take direct advantage of multiple
		1242	CPUs, is often orders of magnitude faster because it shares data using
		1243	real threads, refer to my talk for details).
		1244
		1245	As summary, i-threads *use* threads to implement processes, while
		1246	the compatible forks module *uses* processes to emulate, uhm,
		1247	processes. I-threads slow down every perl program when enabled, and
		1248	outside of windows, serve no (or little) practical purpose, but
		1249	disadvantages every single-threaded Perl program.
		1250
		1251	This is the reason that I try to avoid the name "ithreads", as it is
		1252	misleading as it implies that it implements some kind of thread model for
		1253	perl, and prefer the name "windows process emulation", which describes the
		1254	actual use and behaviour of it much better.
		1255
		1256	=head1 SEE ALSO
		1257
		1258	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		1259
		1260	Debugging: L<Coro::Debug>.
		1261
		1262	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		1263
		1264	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		1265	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		1266
		1267	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		1268
		1269	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		1270	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		1271	L<Coro::Select>.
		1272
		1273	XS API: L<Coro::MakeMaker>.
		1274
		1275	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
		1276
		1277	=head1 AUTHOR
		1278
		1279	Marc Lehmann <schmorp@schmorp.de>
		1280	http://home.schmorp.de/
114		1281
115	=cut	1282	=cut
116		1283
117	sub async(&) {
118	my $pid = new Coro $_[0];
119	$pid->ready;
120	$pid;
121	}
122
123	=item schedule
124
125	Calls the scheduler. Please note that the current process will not be put
126	into the ready queue, so calling this function usually means you will
127	never be called again.
128
129	=cut
130
131	my $prev;
132
133	sub schedule {
134	# should be done using priorities :(
135	($prev, $current) = ($current, shift @ready || $idle);
136	Coro::State::transfer($prev, $current);
137	}
138
139	=item yield
140
141	Yield to other processes. This function puts the current process into the
142	ready queue and calls C<schedule>.
143
144	=cut
145
146	sub yield {
147	$current->ready;
148	&schedule;
149	}
150
151	=item terminate
152
153	Terminates the current process.
154
155	=cut
156
157	sub terminate {
158	&schedule;
159	}
160
161	=back
162
163	# dynamic methods
164
165	=head2 PROCESS METHODS
166
167	These are the methods you can call on process objects.
168
169	=over 4
170
171	=item new Coro \&sub;
172
173	Create a new process and return it. When the sub returns the process
174	automatically terminates. To start the process you must first put it into
175	the ready queue by calling the ready method.
176
177	=cut
178
179	sub new {
180	my $class = shift;
181	my $proc = $_[0];
182	bless {
183	_coro_state => new Coro::State ($proc ? sub { &$proc; &terminate } : $proc),
184	}, $class;
185	}
186
187	=item $process->ready
188
189	Put the current process into the ready queue.
190
191	=cut
192
193	sub ready {
194	push @ready, $_[0];
195	}
196
197	=back
198
199	=cut
200
201	1;
202
203	=head1 SEE ALSO
204
205	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
206	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>.
207
208	=head1 AUTHOR
209
210	Marc Lehmann <pcg@goof.com>
211	http://www.goof.com/pcg/marc/
212
213	=cut
214

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