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

Comparing Coro/Coro.pm (file contents):
Revision 1.3 by root, Tue Jul 3 04:02:31 2001 UTC vs.
Revision 1.128 by root, Wed Sep 19 21:39:15 2007 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - create and manage coroutines	3	Coro - coroutine process abstraction
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use Coro;	7	use Coro;
8		8
9	$new = new Coro sub {	9	async {
10	print "in coroutine, switching back\n";	10	# some asynchronous thread of execution
11	$Coro::main->resume;
12	print "in coroutine again, switching back\n";
13	$Coro::main->resume;
14	};	11	};
15		12
16	print "in main, switching to coroutine\n";	13	# alternatively create an async coroutine like this:
17	$new->resume;	14
18	print "back in main, switch to coroutine again\n";	15	sub some_func : Coro {
19	$new->resume;	16	# some more async code
20	print "back in main\n";	17	}
		18
		19	cede;
21		20
22	=head1 DESCRIPTION	21	=head1 DESCRIPTION
23		22
24	This module implements coroutines. Coroutines, similar to continuations,	23	This module collection manages coroutines. Coroutines are similar
25	allow you to run more than one "thread of execution" in parallel. Unlike	24	to threads but don't run in parallel at the same time even on SMP
26	threads this, only voluntary switching is used so locking problems are	25	machines. The specific flavor of coroutine used in this module also
27	greatly reduced.	26	guarantees you that it will not switch between coroutines unless
		27	necessary, at easily-identified points in your program, so locking and
		28	parallel access are rarely an issue, making coroutine programming much
		29	safer than threads programming.
28		30
29	Although this is the "main" module of the Coro family it provides only	31	(Perl, however, does not natively support real threads but instead does a
30	low-level functionality. See L<Coro::Process> and related modules for a	32	very slow and memory-intensive emulation of processes using threads. This
31	more useful process abstraction including scheduling.	33	is a performance win on Windows machines, and a loss everywhere else).
		34
		35	In this module, coroutines are defined as "callchain + lexical variables +
		36	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
		37	its own set of lexicals and its own set of perls most important global
		38	variables.
		39
		40	=cut
		41
		42	package Coro;
		43
		44	use strict;
		45	no warnings "uninitialized";
		46
		47	use Coro::State;
		48
		49	use base qw(Coro::State Exporter);
		50
		51	our $idle; # idle handler
		52	our $main; # main coroutine
		53	our $current; # current coroutine
		54
		55	our $VERSION = '3.7';
		56
		57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		58	our %EXPORT_TAGS = (
		59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		60	);
		61	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
		62
		63	{
		64	my @async;
		65	my $init;
		66
		67	# this way of handling attributes simply is NOT scalable ;()
		68	sub import {
		69	no strict 'refs';
		70
		71	Coro->export_to_level (1, @_);
		72
		73	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
		74	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
		75	my ($package, $ref) = (shift, shift);
		76	my @attrs;
		77	for (@_) {
		78	if ($_ eq "Coro") {
		79	push @async, $ref;
		80	unless ($init++) {
		81	eval q{
		82	sub INIT {
		83	&async(pop @async) while @async;
		84	}
		85	};
		86	}
		87	} else {
		88	push @attrs, $_;
		89	}
		90	}
		91	return $old ? $old->($package, $ref, @attrs) : @attrs;
		92	};
		93	}
		94
		95	}
32		96
33	=over 4	97	=over 4
34		98
35	=cut
36
37	package Coro;
38
39	BEGIN {
40	$VERSION = 0.01;
41
42	require XSLoader;
43	XSLoader::load Coro, $VERSION;
44	}
45
46	=item $main	99	=item $main
47		100
48	This coroutine represents the main program.	101	This coroutine represents the main program.
49		102
50	=item $current	103	=cut
51		104
		105	$main = new Coro;
		106
		107	=item $current (or as function: current)
		108
52	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	109	The current coroutine (the last coroutine switched to). The initial value
		110	is C<$main> (of course).
53		111
54	=cut	112	This variable is B<strictly> I<read-only>. It is provided for performance
		113	reasons. If performance is not essential you are encouraged to use the
		114	C<Coro::current> function instead.
55		115
56	$main = $current = _newprocess {	116	=cut
57	# never being called	117
		118	# maybe some other module used Coro::Specific before...
		119	$main->{specific} = $current->{specific}
		120	if $current;
		121
		122	_set_current $main;
		123
		124	sub current() { $current }
		125
		126	=item $idle
		127
		128	A callback that is called whenever the scheduler finds no ready coroutines
		129	to run. The default implementation prints "FATAL: deadlock detected" and
		130	exits, because the program has no other way to continue.
		131
		132	This hook is overwritten by modules such as C<Coro::Timer> and
		133	C<Coro::Event> to wait on an external event that hopefully wake up a
		134	coroutine so the scheduler can run it.
		135
		136	Please note that if your callback recursively invokes perl (e.g. for event
		137	handlers), then it must be prepared to be called recursively.
		138
		139	=cut
		140
		141	$idle = sub {
		142	require Carp;
		143	Carp::croak ("FATAL: deadlock detected");
58	};	144	};
59		145
60	=item $error, $error_msg, $error_coro	146	sub _cancel {
		147	my ($self) = @_;
61		148
62	This coroutine will be called on fatal errors. C<$error_msg> and	149	# free coroutine data and mark as destructed
63	C<$error_coro> return the error message and the error-causing coroutine,	150	$self->_destroy
64	respectively.	151	or return;
65		152
66	=cut	153	# call all destruction callbacks
		154	$_->(@{$self->{status}})
		155	for @{(delete $self->{destroy_cb}) \|\| []};
		156	}
67		157
68	$error_msg =	158	# this coroutine is necessary because a coroutine
69	$error_coro = undef;	159	# cannot destroy itself.
		160	my @destroy;
		161	my $manager;
70		162
71	$error = _newprocess {	163	$manager = new Coro sub {
72	print STDERR "FATAL: $error_msg\nprogram aborted\n";	164	while () {
73	exit 250;	165	(shift @destroy)->_cancel
		166	while @destroy;
		167
		168	&schedule;
		169	}
74	};	170	};
75		171
76	=item $coro = new $coderef [, @args]	172	$manager->prio (PRIO_MAX);
77		173
78	Create a new coroutine and return it. The first C<resume> call to this	174	# static methods. not really.
79	coroutine will start execution at the given coderef. If it returns it
80	should return a coroutine to switch to. If, after returning, the coroutine
81	is C<resume>d again it starts execution again at the givne coderef.
82		175
		176	=back
		177
		178	=head2 STATIC METHODS
		179
		180	Static methods are actually functions that operate on the current coroutine only.
		181
		182	=over 4
		183
		184	=item async { ... } [@args...]
		185
		186	Create a new asynchronous coroutine and return it's coroutine object
		187	(usually unused). When the sub returns the new coroutine is automatically
		188	terminated.
		189
		190	Calling C<exit> in a coroutine will do the same as calling exit outside
		191	the coroutine. Likewise, when the coroutine dies, the program will exit,
		192	just as it would in the main program.
		193
		194	# create a new coroutine that just prints its arguments
		195	async {
		196	print "@_\n";
		197	} 1,2,3,4;
		198
83	=cut	199	=cut
		200
		201	sub async(&@) {
		202	my $coro = new Coro @_;
		203	$coro->ready;
		204	$coro
		205	}
		206
		207	=item async_pool { ... } [@args...]
		208
		209	Similar to C<async>, but uses a coroutine pool, so you should not call
		210	terminate or join (although you are allowed to), and you get a coroutine
		211	that might have executed other code already (which can be good or bad :).
		212
		213	Also, the block is executed in an C<eval> context and a warning will be
		214	issued in case of an exception instead of terminating the program, as
		215	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		216	will not work in the expected way, unless you call terminate or cancel,
		217	which somehow defeats the purpose of pooling.
		218
		219	The priority will be reset to C<0> after each job, otherwise the coroutine
		220	will be re-used "as-is".
		221
		222	The pool size is limited to 8 idle coroutines (this can be adjusted by
		223	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		224	required.
		225
		226	If you are concerned about pooled coroutines growing a lot because a
		227	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
		228	terminate }> once per second or so to slowly replenish the pool.
		229
		230	=cut
		231
		232	our $POOL_SIZE = 8;
		233	our @pool;
		234
		235	sub pool_handler {
		236	while () {
		237	eval {
		238	my ($cb, @arg) = @{ delete $current->{_invoke} or return };
		239	$cb->(@arg);
		240	};
		241	warn $@ if $@;
		242
		243	last if @pool >= $POOL_SIZE;
		244	push @pool, $current;
		245
		246	$current->save (Coro::State::SAVE_DEF);
		247	$current->prio (0);
		248	schedule;
		249	}
		250	}
		251
		252	sub async_pool(&@) {
		253	# this is also inlined into the unlock_scheduler
		254	my $coro = (pop @pool) \|\| do {
		255	my $coro = new Coro \&pool_handler;
		256	$coro->{desc} = "async_pool";
		257	$coro
		258	};
		259
		260	$coro->{_invoke} = [@_];
		261	$coro->ready;
		262
		263	$coro
		264	}
		265
		266	=item schedule
		267
		268	Calls the scheduler. Please note that the current coroutine will not be put
		269	into the ready queue, so calling this function usually means you will
		270	never be called again unless something else (e.g. an event handler) calls
		271	ready.
		272
		273	The canonical way to wait on external events is this:
		274
		275	{
		276	# remember current coroutine
		277	my $current = $Coro::current;
		278
		279	# register a hypothetical event handler
		280	on_event_invoke sub {
		281	# wake up sleeping coroutine
		282	$current->ready;
		283	undef $current;
		284	};
		285
		286	# call schedule until event occurred.
		287	# in case we are woken up for other reasons
		288	# (current still defined), loop.
		289	Coro::schedule while $current;
		290	}
		291
		292	=item cede
		293
		294	"Cede" to other coroutines. This function puts the current coroutine into the
		295	ready queue and calls C<schedule>, which has the effect of giving up the
		296	current "timeslice" to other coroutines of the same or higher priority.
		297
		298	Returns true if at least one coroutine switch has happened.
		299
		300	=item Coro::cede_notself
		301
		302	Works like cede, but is not exported by default and will cede to any
		303	coroutine, regardless of priority, once.
		304
		305	Returns true if at least one coroutine switch has happened.
		306
		307	=item terminate [arg...]
		308
		309	Terminates the current coroutine with the given status values (see L<cancel>).
		310
		311	=cut
		312
		313	sub terminate {
		314	$current->cancel (@_);
		315	}
		316
		317	=back
		318
		319	# dynamic methods
		320
		321	=head2 COROUTINE METHODS
		322
		323	These are the methods you can call on coroutine objects.
		324
		325	=over 4
		326
		327	=item new Coro \&sub [, @args...]
		328
		329	Create a new coroutine and return it. When the sub returns the coroutine
		330	automatically terminates as if C<terminate> with the returned values were
		331	called. To make the coroutine run you must first put it into the ready queue
		332	by calling the ready method.
		333
		334	See C<async> for additional discussion.
		335
		336	=cut
		337
		338	sub _run_coro {
		339	terminate &{+shift};
		340	}
84		341
85	sub new {	342	sub new {
86	my $class = $_[0];	343	my $class = shift;
87	my $proc = $_[1];	344
88	bless _newprocess {	345	$class->SUPER::new (\&_run_coro, @_)
89	do {	346	}
90	eval { &$proc->resume };	347
91	if ($@) {	348	=item $success = $coroutine->ready
92	($error_msg, $error_coro) = ($@, $current);	349
93	$error->resume;	350	Put the given coroutine into the ready queue (according to it's priority)
		351	and return true. If the coroutine is already in the ready queue, do nothing
		352	and return false.
		353
		354	=item $is_ready = $coroutine->is_ready
		355
		356	Return wether the coroutine is currently the ready queue or not,
		357
		358	=item $coroutine->cancel (arg...)
		359
		360	Terminates the given coroutine and makes it return the given arguments as
		361	status (default: the empty list). Never returns if the coroutine is the
		362	current coroutine.
		363
		364	=cut
		365
		366	sub cancel {
		367	my $self = shift;
		368	$self->{status} = [@_];
		369
		370	if ($current == $self) {
		371	push @destroy, $self;
		372	$manager->ready;
		373	&schedule while 1;
		374	} else {
		375	$self->_cancel;
		376	}
		377	}
		378
		379	=item $coroutine->join
		380
		381	Wait until the coroutine terminates and return any values given to the
		382	C<terminate> or C<cancel> functions. C<join> can be called multiple times
		383	from multiple coroutine.
		384
		385	=cut
		386
		387	sub join {
		388	my $self = shift;
		389
		390	unless ($self->{status}) {
		391	my $current = $current;
		392
		393	push @{$self->{destroy_cb}}, sub {
		394	$current->ready;
		395	undef $current;
		396	};
		397
		398	&schedule while $current;
		399	}
		400
		401	wantarray ? @{$self->{status}} : $self->{status}[0];
		402	}
		403
		404	=item $coroutine->on_destroy (\&cb)
		405
		406	Registers a callback that is called when this coroutine gets destroyed,
		407	but before it is joined. The callback gets passed the terminate arguments,
		408	if any.
		409
		410	=cut
		411
		412	sub on_destroy {
		413	my ($self, $cb) = @_;
		414
		415	push @{ $self->{destroy_cb} }, $cb;
		416	}
		417
		418	=item $oldprio = $coroutine->prio ($newprio)
		419
		420	Sets (or gets, if the argument is missing) the priority of the
		421	coroutine. Higher priority coroutines get run before lower priority
		422	coroutines. Priorities are small signed integers (currently -4 .. +3),
		423	that you can refer to using PRIO_xxx constants (use the import tag :prio
		424	to get then):
		425
		426	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		427	3 > 1 > 0 > -1 > -3 > -4
		428
		429	# set priority to HIGH
		430	current->prio(PRIO_HIGH);
		431
		432	The idle coroutine ($Coro::idle) always has a lower priority than any
		433	existing coroutine.
		434
		435	Changing the priority of the current coroutine will take effect immediately,
		436	but changing the priority of coroutines in the ready queue (but not
		437	running) will only take effect after the next schedule (of that
		438	coroutine). This is a bug that will be fixed in some future version.
		439
		440	=item $newprio = $coroutine->nice ($change)
		441
		442	Similar to C<prio>, but subtract the given value from the priority (i.e.
		443	higher values mean lower priority, just as in unix).
		444
		445	=item $olddesc = $coroutine->desc ($newdesc)
		446
		447	Sets (or gets in case the argument is missing) the description for this
		448	coroutine. This is just a free-form string you can associate with a coroutine.
		449
		450	=cut
		451
		452	sub desc {
		453	my $old = $_[0]{desc};
		454	$_[0]{desc} = $_[1] if @_ > 1;
		455	$old;
		456	}
		457
		458	=back
		459
		460	=head2 GLOBAL FUNCTIONS
		461
		462	=over 4
		463
		464	=item Coro::nready
		465
		466	Returns the number of coroutines that are currently in the ready state,
		467	i.e. that can be switched to. The value C<0> means that the only runnable
		468	coroutine is the currently running one, so C<cede> would have no effect,
		469	and C<schedule> would cause a deadlock unless there is an idle handler
		470	that wakes up some coroutines.
		471
		472	=item my $guard = Coro::guard { ... }
		473
		474	This creates and returns a guard object. Nothing happens until the object
		475	gets destroyed, in which case the codeblock given as argument will be
		476	executed. This is useful to free locks or other resources in case of a
		477	runtime error or when the coroutine gets canceled, as in both cases the
		478	guard block will be executed. The guard object supports only one method,
		479	C<< ->cancel >>, which will keep the codeblock from being executed.
		480
		481	Example: set some flag and clear it again when the coroutine gets canceled
		482	or the function returns:
		483
		484	sub do_something {
		485	my $guard = Coro::guard { $busy = 0 };
		486	$busy = 1;
		487
		488	# do something that requires $busy to be true
		489	}
		490
		491	=cut
		492
		493	sub guard(&) {
		494	bless \(my $cb = $_[0]), "Coro::guard"
		495	}
		496
		497	sub Coro::guard::cancel {
		498	${$_[0]} = sub { };
		499	}
		500
		501	sub Coro::guard::DESTROY {
		502	${$_[0]}->();
		503	}
		504
		505
		506	=item unblock_sub { ... }
		507
		508	This utility function takes a BLOCK or code reference and "unblocks" it,
		509	returning the new coderef. This means that the new coderef will return
		510	immediately without blocking, returning nothing, while the original code
		511	ref will be called (with parameters) from within its own coroutine.
		512
		513	The reason this function exists is that many event libraries (such as the
		514	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		515	of thread-safety). This means you must not block within event callbacks,
		516	otherwise you might suffer from crashes or worse.
		517
		518	This function allows your callbacks to block by executing them in another
		519	coroutine where it is safe to block. One example where blocking is handy
		520	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		521	disk.
		522
		523	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		524	creating event callbacks that want to block.
		525
		526	=cut
		527
		528	our @unblock_queue;
		529
		530	# we create a special coro because we want to cede,
		531	# to reduce pressure on the coro pool (because most callbacks
		532	# return immediately and can be reused) and because we cannot cede
		533	# inside an event callback.
		534	our $unblock_scheduler = async {
		535	while () {
		536	while (my $cb = pop @unblock_queue) {
		537	# this is an inlined copy of async_pool
		538	my $coro = (pop @pool or new Coro \&pool_handler);
		539
		540	$coro->{_invoke} = $cb;
		541	$coro->ready;
		542	cede; # for short-lived callbacks, this reduces pressure on the coro pool
94	}	543	}
95	} while ();	544	schedule; # sleep well
96	}, $class;	545	}
97	}	546	};
98		547
99	=item $coro->resume	548	sub unblock_sub(&) {
		549	my $cb = shift;
100		550
101	Resume execution at the given coroutine.	551	sub {
102		552	unshift @unblock_queue, [$cb, @_];
103	=cut	553	$unblock_scheduler->ready;
104		554	}
105	my $prev;
106
107	sub resume {
108	$prev = $current; $current = $_[0];
109	_transfer($prev, $current);
110	}	555	}
		556
		557	=back
		558
		559	=cut
111		560
112	1;	561	1;
113		562
114	=back	563	=head1 BUGS/LIMITATIONS
115		564
116	=head1 BUGS	565	- you must make very sure that no coro is still active on global
		566	destruction. very bad things might happen otherwise (usually segfaults).
117		567
118	This module has not yet been extensively tested.	568	- this module is not thread-safe. You should only ever use this module
		569	from the same thread (this requirement might be loosened in the future
		570	to allow per-thread schedulers, but Coro::State does not yet allow
		571	this).
119		572
120	=head1 SEE ALSO	573	=head1 SEE ALSO
121		574
122	L<Coro::Process>, L<Coro::Signal>.	575	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		576
		577	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		578
		579	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		580
		581	Embedding: L<Coro:MakeMaker>
123		582
124	=head1 AUTHOR	583	=head1 AUTHOR
125		584
126	Marc Lehmann <pcg@goof.com>	585	Marc Lehmann <schmorp@schmorp.de>
127	http://www.goof.com/pcg/marc/	586	http://home.schmorp.de/
128		587
129	=cut	588	=cut
130		589

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Comparing Coro/Coro.pm (file contents): Revision 1.3 by root, Tue Jul 3 04:02:31 2001 UTC vs. Revision 1.128 by root, Wed Sep 19 21:39:15 2007 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.3 by root, Tue Jul 3 04:02:31 2001 UTC vs.
Revision 1.128 by root, Wed Sep 19 21:39:15 2007 UTC