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

Comparing Coro/Coro.pm (file contents):
Revision 1.11 by root, Sun Jul 15 03:24:18 2001 UTC vs.
Revision 1.244 by root, Sat Dec 13 22:08:13 2008 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 coroutine
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
		35	in the form of cooperative threads (also called coroutines in the
		36	documentation). They are similar to kernel threads but don't (in general)
		37	run in parallel at the same time even on SMP machines. The specific flavor
		38	of thread offered by this module also guarantees you that it will not
		39	switch between threads unless necessary, at easily-identified points in
		40	your program, so locking and parallel access are rarely an issue, making
		41	thread programming much safer and easier than using other thread models.
		42
		43	Unlike the so-called "Perl threads" (which are not actually real threads
		44	but only the windows process emulation ported to unix), Coro provides a
		45	full shared address space, which makes communication between threads
		46	very easy. And threads are fast, too: disabling the Windows process
		47	emulation code in your perl and using Coro can easily result in a two to
		48	four times speed increase for your programs.
		49
		50	Coro achieves that by supporting multiple running interpreters that share
		51	data, which is especially useful to code pseudo-parallel processes and
		52	for event-based programming, such as multiple HTTP-GET requests running
		53	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		54	into an event-based environment.
		55
		56	In this module, a thread is defined as "callchain + lexical variables +
		57	@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,
		58	its own set of lexicals and its own set of perls most important global
		59	variables (see L<Coro::State> for more configuration and background info).
		60
		61	See also the C<SEE ALSO> section at the end of this document - the Coro
		62	module family is quite large.
		63
23	=cut	64	=cut
24		65
25	package Coro;	66	package Coro;
26		67
		68	use strict qw(vars subs);
		69	no warnings "uninitialized";
		70
27	use Coro::State;	71	use Coro::State;
28		72
29	use base Exporter;	73	use base qw(Coro::State Exporter);
30		74
31	$VERSION = 0.04;	75	our $idle; # idle handler
		76	our $main; # main coroutine
		77	our $current; # current coroutine
32		78
33	@EXPORT = qw(async yield schedule);	79	our $VERSION = 5.13;
34	@EXPORT_OK = qw($current);
35		80
36	{	81	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
37	use subs 'async';	82	our %EXPORT_TAGS = (
		83	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		84	);
		85	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
38		86
39	my @async;	87	=head1 GLOBAL VARIABLES
40		88
41	# this way of handling attributes simply is NOT scalable ;()	89	=over 4
42	sub import {	90
43	Coro->export_to_level(1, @_);	91	=item $Coro::main
44	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};	92
45	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {	93	This variable stores the coroutine object that represents the main
46	my ($package, $ref) = (shift, shift);	94	program. While you cna C<ready> it and do most other things you can do to
47	my @attrs;	95	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
48	for (@_) {	96	whether you are running in the main program or not.
49	if ($_ eq "Coro") {	97
50	push @async, $ref;	98	=cut
51	} else {	99
52	push @attrs, @_;	100	# $main is now being initialised by Coro::State
53	}	101
54	}	102	=item $Coro::current
55	return $old ? $old->($package, $name, @attrs) : @attrs;	103
		104	The coroutine object representing the current coroutine (the last
		105	coroutine that the Coro scheduler switched to). The initial value is
		106	C<$Coro::main> (of course).
		107
		108	This variable is B<strictly> I<read-only>. You can take copies of the
		109	value stored in it and use it as any other coroutine object, but you must
		110	not otherwise modify the variable itself.
		111
		112	=cut
		113
		114	sub current() { $current } # [DEPRECATED]
		115
		116	=item $Coro::idle
		117
		118	This variable is mainly useful to integrate Coro into event loops. It is
		119	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		120	pretty low-level functionality.
		121
		122	This variable stores either a coroutine or a callback.
		123
		124	If it is a callback, the it is called whenever the scheduler finds no
		125	ready coroutines to run. The default implementation prints "FATAL:
		126	deadlock detected" and exits, because the program has no other way to
		127	continue.
		128
		129	If it is a coroutine object, then this object will be readied (without
		130	invoking any ready hooks, however) when the scheduler finds no other ready
		131	coroutines to run.
		132
		133	This hook is overwritten by modules such as C<Coro::EV> and
		134	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
		135	coroutine so the scheduler can run it.
		136
		137	Note that the callback I<must not>, under any circumstances, block
		138	the current coroutine. Normally, this is achieved by having an "idle
		139	coroutine" that calls the event loop and then blocks again, and then
		140	readying that coroutine in the idle handler, or by simply placing the idle
		141	coroutine in this variable.
		142
		143	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		144	technique.
		145
		146	Please note that if your callback recursively invokes perl (e.g. for event
		147	handlers), then it must be prepared to be called recursively itself.
		148
		149	=cut
		150
		151	$idle = sub {
		152	require Carp;
		153	Carp::croak ("FATAL: deadlock detected");
		154	};
		155
		156	# this coroutine is necessary because a coroutine
		157	# cannot destroy itself.
		158	our @destroy;
		159	our $manager;
		160
		161	$manager = new Coro sub {
		162	while () {
		163	Coro::_cancel shift @destroy
		164	while @destroy;
		165
		166	&schedule;
		167	}
		168	};
		169	$manager->{desc} = "[coro manager]";
		170	$manager->prio (PRIO_MAX);
		171
		172	=back
		173
		174	=head1 SIMPLE COROUTINE CREATION
		175
		176	=over 4
		177
		178	=item async { ... } [@args...]
		179
		180	Create a new coroutine and return its coroutine object (usually
		181	unused). The coroutine will be put into the ready queue, so
		182	it will start running automatically on the next scheduler run.
		183
		184	The first argument is a codeblock/closure that should be executed in the
		185	coroutine. When it returns argument returns the coroutine is automatically
		186	terminated.
		187
		188	The remaining arguments are passed as arguments to the closure.
		189
		190	See the C<Coro::State::new> constructor for info about the coroutine
		191	environment in which coroutines are executed.
		192
		193	Calling C<exit> in a coroutine will do the same as calling exit outside
		194	the coroutine. Likewise, when the coroutine dies, the program will exit,
		195	just as it would in the main program.
		196
		197	If you do not want that, you can provide a default C<die> handler, or
		198	simply avoid dieing (by use of C<eval>).
		199
		200	Example: Create a new coroutine that just prints its arguments.
		201
		202	async {
		203	print "@_\n";
		204	} 1,2,3,4;
		205
		206	=cut
		207
		208	sub async(&@) {
		209	my $coro = new Coro @_;
		210	$coro->ready;
		211	$coro
		212	}
		213
		214	=item async_pool { ... } [@args...]
		215
		216	Similar to C<async>, but uses a coroutine pool, so you should not call
		217	terminate or join on it (although you are allowed to), and you get a
		218	coroutine that might have executed other code already (which can be good
		219	or bad :).
		220
		221	On the plus side, this function is about twice as fast as creating (and
		222	destroying) a completely new coroutine, so if you need a lot of generic
		223	coroutines in quick successsion, use C<async_pool>, not C<async>.
		224
		225	The code block is executed in an C<eval> context and a warning will be
		226	issued in case of an exception instead of terminating the program, as
		227	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		228	will not work in the expected way, unless you call terminate or cancel,
		229	which somehow defeats the purpose of pooling (but is fine in the
		230	exceptional case).
		231
		232	The priority will be reset to C<0> after each run, tracing will be
		233	disabled, the description will be reset and the default output filehandle
		234	gets restored, so you can change all these. Otherwise the coroutine will
		235	be re-used "as-is": most notably if you change other per-coroutine global
		236	stuff such as C<$/> you I<must needs> revert that change, which is most
		237	simply done by using local as in: C<< local $/ >>.
		238
		239	The idle pool size is limited to C<8> idle coroutines (this can be
		240	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		241	coros as required.
		242
		243	If you are concerned about pooled coroutines growing a lot because a
		244	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		245	{ terminate }> once per second or so to slowly replenish the pool. In
		246	addition to that, when the stacks used by a handler grows larger than 32kb
		247	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		248
		249	=cut
		250
		251	our $POOL_SIZE = 8;
		252	our $POOL_RSS = 32 * 1024;
		253	our @async_pool;
		254
		255	sub pool_handler {
		256	while () {
		257	eval {
		258	&{&_pool_handler} while 1;
56	};	259	};
57	}
58		260
59	sub INIT {	261	warn $@ if $@;
60	async pop @async while @async;
61	}	262	}
62	}	263	}
63		264
64	=item $main	265	=back
65		266
66	This coroutine represents the main program.	267	=head1 STATIC METHODS
67		268
68	=cut	269	Static methods are actually functions that implicitly operate on the
		270	current coroutine.
69		271
70	our $main = new Coro;	272	=over 4
71		273
72	=item $current	274	=item schedule
73		275
74	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	276	Calls the scheduler. The scheduler will find the next coroutine that is
		277	to be run from the ready queue and switches to it. The next coroutine
		278	to be run is simply the one with the highest priority that is longest
		279	in its ready queue. If there is no coroutine ready, it will clal the
		280	C<$Coro::idle> hook.
75		281
76	=cut	282	Please note that the current coroutine will I<not> be put into the ready
		283	queue, so calling this function usually means you will never be called
		284	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		285	thus waking you up.
77		286
78	# maybe some other module used Coro::Specific before...	287	This makes C<schedule> I<the> generic method to use to block the current
79	if ($current) {	288	coroutine and wait for events: first you remember the current coroutine in
80	$main->{specific} = $current->{specific};	289	a variable, then arrange for some callback of yours to call C<< ->ready
81	}	290	>> on that once some event happens, and last you call C<schedule> to put
		291	yourself to sleep. Note that a lot of things can wake your coroutine up,
		292	so you need to check whether the event indeed happened, e.g. by storing the
		293	status in a variable.
82		294
83	our $current = $main;	295	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
84		296
85	=item $idle	297	=item cede
86		298
87	The coroutine to switch to when no other coroutine is running. The default	299	"Cede" to other coroutines. This function puts the current coroutine into
88	implementation prints "FATAL: deadlock detected" and exits.	300	the ready queue and calls C<schedule>, which has the effect of giving
		301	up the current "timeslice" to other coroutines of the same or higher
		302	priority. Once your coroutine gets its turn again it will automatically be
		303	resumed.
89		304
90	=cut	305	This function is often called C<yield> in other languages.
91		306
92	# should be done using priorities :(	307	=item Coro::cede_notself
		308
		309	Works like cede, but is not exported by default and will cede to I<any>
		310	coroutine, regardless of priority. This is useful sometimes to ensure
		311	progress is made.
		312
		313	=item terminate [arg...]
		314
		315	Terminates the current coroutine with the given status values (see L<cancel>).
		316
		317	=item killall
		318
		319	Kills/terminates/cancels all coroutines except the currently running
		320	one. This is useful after a fork, either in the child or the parent, as
		321	usually only one of them should inherit the running coroutines.
		322
		323	Note that while this will try to free some of the main programs resources,
		324	you cannot free all of them, so if a coroutine that is not the main
		325	program calls this function, there will be some one-time resource leak.
		326
		327	=cut
		328
		329	sub killall {
		330	for (Coro::State::list) {
		331	$_->cancel
		332	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		333	}
		334	}
		335
		336	=back
		337
		338	=head1 COROUTINE OBJECT METHODS
		339
		340	These are the methods you can call on coroutine objects (or to create
		341	them).
		342
		343	=over 4
		344
		345	=item new Coro \&sub [, @args...]
		346
		347	Create a new coroutine and return it. When the sub returns, the coroutine
		348	automatically terminates as if C<terminate> with the returned values were
		349	called. To make the coroutine run you must first put it into the ready
		350	queue by calling the ready method.
		351
		352	See C<async> and C<Coro::State::new> for additional info about the
		353	coroutine environment.
		354
		355	=cut
		356
		357	sub _coro_run {
		358	terminate &{+shift};
		359	}
		360
		361	=item $success = $coroutine->ready
		362
		363	Put the given coroutine into the end of its ready queue (there is one
		364	queue for each priority) and return true. If the coroutine is already in
		365	the ready queue, do nothing and return false.
		366
		367	This ensures that the scheduler will resume this coroutine automatically
		368	once all the coroutines of higher priority and all coroutines of the same
		369	priority that were put into the ready queue earlier have been resumed.
		370
		371	=item $is_ready = $coroutine->is_ready
		372
		373	Return whether the coroutine is currently the ready queue or not,
		374
		375	=item $coroutine->cancel (arg...)
		376
		377	Terminates the given coroutine and makes it return the given arguments as
		378	status (default: the empty list). Never returns if the coroutine is the
		379	current coroutine.
		380
		381	=cut
		382
		383	sub cancel {
		384	my $self = shift;
		385
		386	if ($current == $self) {
		387	terminate @_;
		388	} else {
		389	$self->{_status} = [@_];
		390	$self->_cancel;
		391	}
		392	}
		393
		394	=item $coroutine->schedule_to
		395
		396	Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
		397	of continuing with the next coro from the ready queue, always switch to
		398	the given coroutine object (regardless of priority etc.). The readyness
		399	state of that coroutine isn't changed.
		400
		401	This is an advanced method for special cases - I'd love to hear about any
		402	uses for this one.
		403
		404	=item $coroutine->cede_to
		405
		406	Like C<schedule_to>, but puts the current coroutine into the ready
		407	queue. This has the effect of temporarily switching to the given
		408	coroutine, and continuing some time later.
		409
		410	This is an advanced method for special cases - I'd love to hear about any
		411	uses for this one.
		412
		413	=item $coroutine->throw ([$scalar])
		414
		415	If C<$throw> is specified and defined, it will be thrown as an exception
		416	inside the coroutine at the next convenient point in time. Otherwise
		417	clears the exception object.
		418
		419	Coro will check for the exception each time a schedule-like-function
		420	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		421	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		422	detect this case and return early in case an exception is pending.
		423
		424	The exception object will be thrown "as is" with the specified scalar in
		425	C<$@>, i.e. if it is a string, no line number or newline will be appended
		426	(unlike with C<die>).
		427
		428	This can be used as a softer means than C<cancel> to ask a coroutine to
		429	end itself, although there is no guarantee that the exception will lead to
		430	termination, and if the exception isn't caught it might well end the whole
		431	program.
		432
		433	You might also think of C<throw> as being the moral equivalent of
		434	C<kill>ing a coroutine with a signal (in this case, a scalar).
		435
		436	=item $coroutine->join
		437
		438	Wait until the coroutine terminates and return any values given to the
		439	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		440	from multiple coroutines, and all will be resumed and given the status
		441	return once the C<$coroutine> terminates.
		442
		443	=cut
		444
		445	sub join {
		446	my $self = shift;
		447
		448	unless ($self->{_status}) {
		449	my $current = $current;
		450
		451	push @{$self->{_on_destroy}}, sub {
		452	$current->ready;
		453	undef $current;
		454	};
		455
		456	&schedule while $current;
		457	}
		458
		459	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		460	}
		461
		462	=item $coroutine->on_destroy (\&cb)
		463
		464	Registers a callback that is called when this coroutine gets destroyed,
		465	but before it is joined. The callback gets passed the terminate arguments,
		466	if any, and I<must not> die, under any circumstances.
		467
		468	=cut
		469
		470	sub on_destroy {
		471	my ($self, $cb) = @_;
		472
		473	push @{ $self->{_on_destroy} }, $cb;
		474	}
		475
		476	=item $oldprio = $coroutine->prio ($newprio)
		477
		478	Sets (or gets, if the argument is missing) the priority of the
		479	coroutine. Higher priority coroutines get run before lower priority
		480	coroutines. Priorities are small signed integers (currently -4 .. +3),
		481	that you can refer to using PRIO_xxx constants (use the import tag :prio
		482	to get then):
		483
		484	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		485	3 > 1 > 0 > -1 > -3 > -4
		486
		487	# set priority to HIGH
		488	current->prio(PRIO_HIGH);
		489
		490	The idle coroutine ($Coro::idle) always has a lower priority than any
		491	existing coroutine.
		492
		493	Changing the priority of the current coroutine will take effect immediately,
		494	but changing the priority of coroutines in the ready queue (but not
		495	running) will only take effect after the next schedule (of that
		496	coroutine). This is a bug that will be fixed in some future version.
		497
		498	=item $newprio = $coroutine->nice ($change)
		499
		500	Similar to C<prio>, but subtract the given value from the priority (i.e.
		501	higher values mean lower priority, just as in unix).
		502
		503	=item $olddesc = $coroutine->desc ($newdesc)
		504
		505	Sets (or gets in case the argument is missing) the description for this
		506	coroutine. This is just a free-form string you can associate with a
		507	coroutine.
		508
		509	This method simply sets the C<< $coroutine->{desc} >> member to the given
		510	string. You can modify this member directly if you wish.
		511
		512	=cut
		513
		514	sub desc {
		515	my $old = $_[0]{desc};
		516	$_[0]{desc} = $_[1] if @_ > 1;
		517	$old;
		518	}
		519
		520	sub transfer {
		521	require Carp;
		522	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		523	}
		524
		525	=back
		526
		527	=head1 GLOBAL FUNCTIONS
		528
		529	=over 4
		530
		531	=item Coro::nready
		532
		533	Returns the number of coroutines that are currently in the ready state,
		534	i.e. that can be switched to by calling C<schedule> directory or
		535	indirectly. The value C<0> means that the only runnable coroutine is the
		536	currently running one, so C<cede> would have no effect, and C<schedule>
		537	would cause a deadlock unless there is an idle handler that wakes up some
		538	coroutines.
		539
		540	=item my $guard = Coro::guard { ... }
		541
		542	This function still exists, but is deprecated. Please use the
		543	C<Guard::guard> function instead.
		544
		545	=cut
		546
		547	BEGIN { *guard = \&Guard::guard }
		548
		549	=item unblock_sub { ... }
		550
		551	This utility function takes a BLOCK or code reference and "unblocks" it,
		552	returning a new coderef. Unblocking means that calling the new coderef
		553	will return immediately without blocking, returning nothing, while the
		554	original code ref will be called (with parameters) from within another
		555	coroutine.
		556
		557	The reason this function exists is that many event libraries (such as the
		558	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		559	of reentrancy). This means you must not block within event callbacks,
		560	otherwise you might suffer from crashes or worse. The only event library
		561	currently known that is safe to use without C<unblock_sub> is L<EV>.
		562
		563	This function allows your callbacks to block by executing them in another
		564	coroutine where it is safe to block. One example where blocking is handy
		565	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		566	disk, for example.
		567
		568	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		569	creating event callbacks that want to block.
		570
		571	If your handler does not plan to block (e.g. simply sends a message to
		572	another coroutine, or puts some other coroutine into the ready queue),
		573	there is no reason to use C<unblock_sub>.
		574
		575	Note that you also need to use C<unblock_sub> for any other callbacks that
		576	are indirectly executed by any C-based event loop. For example, when you
		577	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		578	provides callbacks that are the result of some event callback, then you
		579	must not block either, or use C<unblock_sub>.
		580
		581	=cut
		582
		583	our @unblock_queue;
		584
		585	# we create a special coro because we want to cede,
		586	# to reduce pressure on the coro pool (because most callbacks
		587	# return immediately and can be reused) and because we cannot cede
		588	# inside an event callback.
93	our $idle = new Coro sub {	589	our $unblock_scheduler = new Coro sub {
94	print STDERR "FATAL: deadlock detected\n";	590	while () {
95	exit(51);	591	while (my $cb = pop @unblock_queue) {
		592	&async_pool (@$cb);
		593
		594	# for short-lived callbacks, this reduces pressure on the coro pool
		595	# as the chance is very high that the async_poll coro will be back
		596	# in the idle state when cede returns
		597	cede;
		598	}
		599	schedule; # sleep well
		600	}
96	};	601	};
		602	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
97		603
98	# we really need priorities...	604	sub unblock_sub(&) {
99	my @ready = (); # the ready queue. hehe, rather broken ;)	605	my $cb = shift;
100		606
101	# static methods. not really.	607	sub {
		608	unshift @unblock_queue, [$cb, @_];
		609	$unblock_scheduler->ready;
		610	}
		611	}
102		612
103	=head2 STATIC METHODS	613	=item $cb = Coro::rouse_cb
104		614
105	Static methods are actually functions that operate on the current process only.	615	Create and return a "rouse callback". That's a code reference that,
		616	when called, will remember a copy of its arguments and notify the owner
		617	coroutine of the callback.
		618
		619	See the next function.
		620
		621	=item @args = Coro::rouse_wait [$cb]
		622
		623	Wait for the specified rouse callback (or the last one that was created in
		624	this coroutine).
		625
		626	As soon as the callback is invoked (or when the callback was invoked
		627	before C<rouse_wait>), it will return the arguments originally passed to
		628	the rouse callback.
		629
		630	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		631
		632	=back
		633
		634	=cut
		635
		636	1;
		637
		638	=head1 HOW TO WAIT FOR A CALLBACK
		639
		640	It is very common for a coroutine to wait for some callback to be
		641	called. This occurs naturally when you use coroutines in an otherwise
		642	event-based program, or when you use event-based libraries.
		643
		644	These typically register a callback for some event, and call that callback
		645	when the event occured. In a coroutine, however, you typically want to
		646	just wait for the event, simplyifying things.
		647
		648	For example C<< AnyEvent->child >> registers a callback to be called when
		649	a specific child has exited:
		650
		651	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		652
		653	But from withina coroutine, you often just want to write this:
		654
		655	my $status = wait_for_child $pid;
		656
		657	Coro offers two functions specifically designed to make this easy,
		658	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		659
		660	The first function, C<rouse_cb>, generates and returns a callback that,
		661	when invoked, will save its arguments and notify the coroutine that
		662	created the callback.
		663
		664	The second function, C<rouse_wait>, waits for the callback to be called
		665	(by calling C<schedule> to go to sleep) and returns the arguments
		666	originally passed to the callback.
		667
		668	Using these functions, it becomes easy to write the C<wait_for_child>
		669	function mentioned above:
		670
		671	sub wait_for_child($) {
		672	my ($pid) = @_;
		673
		674	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		675
		676	my ($rpid, $rstatus) = Coro::rouse_wait;
		677	$rstatus
		678	}
		679
		680	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		681	you can roll your own, using C<schedule>:
		682
		683	sub wait_for_child($) {
		684	my ($pid) = @_;
		685
		686	# store the current coroutine in $current,
		687	# and provide result variables for the closure passed to ->child
		688	my $current = $Coro::current;
		689	my ($done, $rstatus);
		690
		691	# pass a closure to ->child
		692	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		693	$rstatus = $_[1]; # remember rstatus
		694	$done = 1; # mark $rstatus as valud
		695	});
		696
		697	# wait until the closure has been called
		698	schedule while !$done;
		699
		700	$rstatus
		701	}
		702
		703
		704	=head1 BUGS/LIMITATIONS
106		705
107	=over 4	706	=over 4
108		707
109	=item async { ... };	708	=item fork with pthread backend
110		709
111	Create a new asynchronous process and return it's process object	710	When Coro is compiled using the pthread backend (which isn't recommended
112	(usually unused). When the sub returns the new process is automatically	711	but required on many BSDs as their libcs are completely broken), then
113	terminated.	712	coroutines will not survive a fork. There is no known workaround except to
		713	fix your libc and use a saner backend.
114		714
115	=cut	715	=item perl process emulation ("threads")
116		716
117	sub async(&) {	717	This module is not perl-pseudo-thread-safe. You should only ever use this
118	my $pid = new Coro $_[0];	718	module from the first thread (this requirement might be removed in the
119	$pid->ready;	719	future to allow per-thread schedulers, but Coro::State does not yet allow
120	$pid;	720	this). I recommend disabling thread support and using processes, as having
121	}	721	the windows process emulation enabled under unix roughly halves perl
		722	performance, even when not used.
122		723
123	=item schedule	724	=item coroutine switching not signal safe
124		725
125	Calls the scheduler. Please note that the current process will not be put	726	You must not switch to another coroutine from within a signal handler
126	into the ready queue, so calling this function usually means you will	727	(only relevant with %SIG - most event libraries provide safe signals).
127	never be called again.
128		728
129	=cut	729	That means you I<MUST NOT> call any function that might "block" the
130		730	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
131	my $prev;	731	anything that calls those. Everything else, including calling C<ready>,
132		732	works.
133	sub schedule {
134	# should be done using priorities :(
135	($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		733
161	=back	734	=back
162		735
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 \⊂
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		736
203	=head1 SEE ALSO	737	=head1 SEE ALSO
204		738
205	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	739	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
206	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>.	740
		741	Debugging: L<Coro::Debug>.
		742
		743	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		744
		745	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		746	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		747
		748	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		749
		750	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		751	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		752	L<Coro::Select>.
		753
		754	XS API: L<Coro::MakeMaker>.
		755
		756	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
207		757
208	=head1 AUTHOR	758	=head1 AUTHOR
209		759
210	Marc Lehmann <pcg@goof.com>	760	Marc Lehmann <schmorp@schmorp.de>
211	http://www.goof.com/pcg/marc/	761	http://home.schmorp.de/
212		762
213	=cut	763	=cut
214		764

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Comparing Coro/Coro.pm (file contents):
Revision 1.11 by root, Sun Jul 15 03:24:18 2001 UTC vs.
Revision 1.244 by root, Sat Dec 13 22:08:13 2008 UTC