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

Comparing Coro/Coro.pm (file contents):
Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs.
Revision 1.105 by root, Fri Jan 5 16:55:01 2007 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - create and manage simple 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	$new->transfer($main);
12	print "in coroutine again, switching back\n";
13	$new->transfer($main);
14	};	11	};
15		12
16	$main = new Coro;	13	# alternatively create an async coroutine like this:
17		14
18	print "in main, switching to coroutine\n";	15	sub some_func : Coro {
19	$main->transfer($new);	16	# some more async code
20	print "back in main, switch to coroutine again\n";	17	}
21	$main->transfer($new);	18
22	print "back in main\n";	19	cede;
23		20
24	=head1 DESCRIPTION	21	=head1 DESCRIPTION
25		22
26	This module implements coroutines. Coroutines, similar to continuations,	23	This module collection manages coroutines. Coroutines are similar
27	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
28	threads this, only voluntary switching is used so locking problems are	25	machines. The specific flavor of coroutine use din this module also
29	greatly reduced.	26	guarentees 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.
30		30
31	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
32	low-level functionality. See L<Coro::Process> and related modules for a	32	very slow and memory-intensive emulation of processes using threads. This
33	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 $VERSION = '3.3';
		56
		57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		58	our %EXPORT_TAGS = (
		59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		60	);
		61	our @EXPORT_OK = (@{$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	}
34		96
35	=over 4	97	=over 4
36		98
37	=cut	99	=item $main
38		100
39	package Coro;	101	This coroutine represents the main program.
40		102
41	BEGIN {	103	=cut
42	$VERSION = 0.03;
43		104
		105	$main = new Coro;
		106
		107	=item $current (or as function: current)
		108
		109	The current coroutine (the last coroutine switched to). The initial value
		110	is C<$main> (of course).
		111
		112	This variable is B<strictly> I<read-only>. It is provided for performance
		113	reasons. If performance is not essentiel you are encouraged to use the
		114	C<Coro::current> function instead.
		115
		116	=cut
		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 {
44	require XSLoader;	142	require Carp;
45	XSLoader::load Coro, $VERSION;	143	Carp::croak ("FATAL: deadlock detected");
46	}	144	};
47		145
48	=item $coro = new [$coderef [, @args]]	146	sub _cancel {
		147	my ($self) = @_;
49		148
50	Create a new coroutine and return it. The first C<transfer> call to this	149	# free coroutine data and mark as destructed
51	coroutine will start execution at the given coderef. If, the subroutine	150	$self->_destroy
52	returns it will be executed again.	151	or return;
53		152
54	If the coderef is omitted this function will create a new "empty"	153	# call all destruction callbacks
55	coroutine, i.e. a coroutine that cannot be transfered to but can be used	154	$_->(@{$self->{status}})
56	to save the current coroutine in.	155	for @{(delete $self->{destroy_cb}) \|\| []};
		156	}
57		157
		158	# this coroutine is necessary because a coroutine
		159	# cannot destroy itself.
		160	my @destroy;
		161	my $manager;
		162
		163	$manager = new Coro sub {
		164	while () {
		165	(shift @destroy)->_cancel
		166	while @destroy;
		167
		168	&schedule;
		169	}
		170	};
		171
		172	$manager->prio (PRIO_MAX);
		173
		174	# static methods. not really.
		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 not work correctly, so do not do that.
		191
		192	When the coroutine dies, the program will exit, just as in the main
		193	program.
		194
		195	# create a new coroutine that just prints its arguments
		196	async {
		197	print "@_\n";
		198	} 1,2,3,4;
		199
58	=cut	200	=cut
		201
		202	sub async(&@) {
		203	my $coro = new Coro @_;
		204	$coro->ready;
		205	$coro
		206	}
		207
		208	=item async_pool { ... } [@args...]
		209
		210	Similar to C<async>, but uses a coroutine pool, so you should not call
		211	terminate or join (although you are allowed to), and you get a coroutine
		212	that might have executed other code already (which can be good or bad :).
		213
		214	Also, the block is executed in an C<eval> context and a warning will be
		215	issued in case of an exception instead of terminating the program, as C<async> does.
		216
		217	The priority will be reset to C<0> after each job, otherwise the coroutine
		218	will be re-used "as-is".
		219
		220	The pool size is limited to 8 idle coroutines (this can be adjusted by
		221	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		222	required.
		223
		224	If you are concerned about pooled coroutines growing a lot because a
		225	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
		226	terminate }> once per second or so to slowly replenish the pool.
		227
		228	=cut
		229
		230	our $POOL_SIZE = 8;
		231	our @pool;
		232
		233	sub pool_handler {
		234	while () {
		235	my ($cb, @arg) = @{ delete $current->{_invoke} };
		236
		237	eval {
		238	$cb->(@arg);
		239	};
		240	warn $@ if $@;
		241
		242	last if @pool >= $POOL_SIZE;
		243	push @pool, $current;
		244
		245	$current->prio (0);
		246	schedule;
		247	}
		248	}
		249
		250	sub async_pool(&@) {
		251	# this is also inlined into the unlock_scheduler
		252	my $coro = (pop @pool or new Coro \&pool_handler);
		253
		254	$coro->{_invoke} = [@_];
		255	$coro->ready;
		256
		257	$coro
		258	}
		259
		260	=item schedule
		261
		262	Calls the scheduler. Please note that the current coroutine will not be put
		263	into the ready queue, so calling this function usually means you will
		264	never be called again unless something else (e.g. an event handler) calls
		265	ready.
		266
		267	The canonical way to wait on external events is this:
		268
		269	{
		270	# remember current coroutine
		271	my $current = $Coro::current;
		272
		273	# register a hypothetical event handler
		274	on_event_invoke sub {
		275	# wake up sleeping coroutine
		276	$current->ready;
		277	undef $current;
		278	};
		279
		280	# call schedule until event occured.
		281	# in case we are woken up for other reasons
		282	# (current still defined), loop.
		283	Coro::schedule while $current;
		284	}
		285
		286	=item cede
		287
		288	"Cede" to other coroutines. This function puts the current coroutine into the
		289	ready queue and calls C<schedule>, which has the effect of giving up the
		290	current "timeslice" to other coroutines of the same or higher priority.
		291
		292	=item Coro::cede_notself
		293
		294	Works like cede, but is not exported by default and will cede to any
		295	coroutine, regardless of priority, once.
		296
		297	=item terminate [arg...]
		298
		299	Terminates the current coroutine with the given status values (see L<cancel>).
		300
		301	=cut
		302
		303	sub terminate {
		304	$current->cancel (@_);
		305	}
		306
		307	=back
		308
		309	# dynamic methods
		310
		311	=head2 COROUTINE METHODS
		312
		313	These are the methods you can call on coroutine objects.
		314
		315	=over 4
		316
		317	=item new Coro \&sub [, @args...]
		318
		319	Create a new coroutine and return it. When the sub returns the coroutine
		320	automatically terminates as if C<terminate> with the returned values were
		321	called. To make the coroutine run you must first put it into the ready queue
		322	by calling the ready method.
		323
		324	Calling C<exit> in a coroutine will not work correctly, so do not do that.
		325
		326	=cut
		327
		328	sub _run_coro {
		329	terminate &{+shift};
		330	}
59		331
60	sub new {	332	sub new {
61	my $class = $_[0];	333	my $class = shift;
62	my $proc = $_[1] \|\| sub { die "tried to transfer to an empty coroutine" };
63	bless _newprocess {
64	do {
65	eval { &$proc };
66	if ($@) {
67	$error_msg = $@;
68	$error_coro = _newprocess { };
69	&transfer($error_coro, $error);
70	}
71	} while (1);
72	}, $class;
73	}
74		334
75	=item $prev->transfer($next)	335	$class->SUPER::new (\&_run_coro, @_)
		336	}
76		337
77	Save the state of the current subroutine in C<$prev> and switch to the	338	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		339
80	The "state" of a subroutine only ever includes scope, i.e. lexical	340	Put the given coroutine into the ready queue (according to it's priority)
81	variables and the current execution state. It does not save/restore any	341	and return true. If the coroutine is already in the ready queue, do nothing
82	global variables such as C<$_> or C<$@> or any other special or non	342	and return false.
83	special variables. So remember that every function call that might call
84	C<transfer> (such as C<Coro::Channel::put>) might clobber any global
85	and/or special variables. Yes, this is by design ;) You cna always create
86	your own process abstraction model that saves these variables.
87		343
88	The easiest way to do this is to create your own scheduling primitive like this:	344	=item $is_ready = $coroutine->is_ready
89		345
90	sub schedule {	346	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	347
92	$old->transfer($new);	348	=item $coroutine->cancel (arg...)
		349
		350	Terminates the given coroutine and makes it return the given arguments as
		351	status (default: the empty list). Never returns if the coroutine is the
		352	current coroutine.
		353
		354	=cut
		355
		356	sub cancel {
		357	my $self = shift;
		358	$self->{status} = [@_];
		359
		360	if ($current == $self) {
		361	push @destroy, $self;
		362	$manager->ready;
		363	&schedule while 1;
		364	} else {
		365	$self->_cancel;
93	}	366	}
94
95	=cut
96
97	# I call the _transfer function from a perl function
98	# because that way perl saves all important things on
99	# the stack. Actually, I'd do it from within XS, but
100	# I couldn't get it to work.
101	sub transfer {
102	_transfer($_[0], $_[1]);
103	}	367	}
104		368
105	=item $error, $error_msg, $error_coro	369	=item $coroutine->join
106		370
107	This coroutine will be called on fatal errors. C<$error_msg> and	371	Wait until the coroutine terminates and return any values given to the
108	C<$error_coro> return the error message and the error-causing coroutine	372	C<terminate> or C<cancel> functions. C<join> can be called multiple times
109	(NOT an object) respectively. This API might change.	373	from multiple coroutine.
110		374
111	=cut	375	=cut
112		376
113	$error_msg =	377	sub join {
114	$error_coro = undef;	378	my $self = shift;
115		379
116	$error = _newprocess {	380	unless ($self->{status}) {
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	381	my $current = $current;
118	exit 50;	382
		383	push @{$self->{destroy_cb}}, sub {
		384	$current->ready;
		385	undef $current;
		386	};
		387
		388	&schedule while $current;
		389	}
		390
		391	wantarray ? @{$self->{status}} : $self->{status}[0];
		392	}
		393
		394	=item $coroutine->on_destroy (\&cb)
		395
		396	Registers a callback that is called when this coroutine gets destroyed,
		397	but before it is joined. The callback gets passed the terminate arguments,
		398	if any.
		399
		400	=cut
		401
		402	sub on_destroy {
		403	my ($self, $cb) = @_;
		404
		405	push @{ $self->{destroy_cb} }, $cb;
		406	}
		407
		408	=item $oldprio = $coroutine->prio ($newprio)
		409
		410	Sets (or gets, if the argument is missing) the priority of the
		411	coroutine. Higher priority coroutines get run before lower priority
		412	coroutines. Priorities are small signed integers (currently -4 .. +3),
		413	that you can refer to using PRIO_xxx constants (use the import tag :prio
		414	to get then):
		415
		416	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		417	3 > 1 > 0 > -1 > -3 > -4
		418
		419	# set priority to HIGH
		420	current->prio(PRIO_HIGH);
		421
		422	The idle coroutine ($Coro::idle) always has a lower priority than any
		423	existing coroutine.
		424
		425	Changing the priority of the current coroutine will take effect immediately,
		426	but changing the priority of coroutines in the ready queue (but not
		427	running) will only take effect after the next schedule (of that
		428	coroutine). This is a bug that will be fixed in some future version.
		429
		430	=item $newprio = $coroutine->nice ($change)
		431
		432	Similar to C<prio>, but subtract the given value from the priority (i.e.
		433	higher values mean lower priority, just as in unix).
		434
		435	=item $olddesc = $coroutine->desc ($newdesc)
		436
		437	Sets (or gets in case the argument is missing) the description for this
		438	coroutine. This is just a free-form string you can associate with a coroutine.
		439
		440	=cut
		441
		442	sub desc {
		443	my $old = $_[0]{desc};
		444	$_[0]{desc} = $_[1] if @_ > 1;
		445	$old;
		446	}
		447
		448	=back
		449
		450	=head2 GLOBAL FUNCTIONS
		451
		452	=over 4
		453
		454	=item Coro::nready
		455
		456	Returns the number of coroutines that are currently in the ready state,
		457	i.e. that can be swicthed to. The value C<0> means that the only runnable
		458	coroutine is the currently running one, so C<cede> would have no effect,
		459	and C<schedule> would cause a deadlock unless there is an idle handler
		460	that wakes up some coroutines.
		461
		462	=item my $guard = Coro::guard { ... }
		463
		464	This creates and returns a guard object. Nothing happens until the objetc
		465	gets destroyed, in which case the codeblock given as argument will be
		466	executed. This is useful to free locks or other resources in case of a
		467	runtime error or when the coroutine gets canceled, as in both cases the
		468	guard block will be executed. The guard object supports only one method,
		469	C<< ->cancel >>, which will keep the codeblock from being executed.
		470
		471	Example: set some flag and clear it again when the coroutine gets canceled
		472	or the function returns:
		473
		474	sub do_something {
		475	my $guard = Coro::guard { $busy = 0 };
		476	$busy = 1;
		477
		478	# do something that requires $busy to be true
		479	}
		480
		481	=cut
		482
		483	sub guard(&) {
		484	bless \(my $cb = $_[0]), "Coro::guard"
		485	}
		486
		487	sub Coro::guard::cancel {
		488	${$_[0]} = sub { };
		489	}
		490
		491	sub Coro::guard::DESTROY {
		492	${$_[0]}->();
		493	}
		494
		495
		496	=item unblock_sub { ... }
		497
		498	This utility function takes a BLOCK or code reference and "unblocks" it,
		499	returning the new coderef. This means that the new coderef will return
		500	immediately without blocking, returning nothing, while the original code
		501	ref will be called (with parameters) from within its own coroutine.
		502
		503	The reason this fucntion exists is that many event libraries (such as the
		504	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		505	of thread-safety). This means you must not block within event callbacks,
		506	otherwise you might suffer from crashes or worse.
		507
		508	This function allows your callbacks to block by executing them in another
		509	coroutine where it is safe to block. One example where blocking is handy
		510	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		511	disk.
		512
		513	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		514	creating event callbacks that want to block.
		515
		516	=cut
		517
		518	our @unblock_queue;
		519
		520	# we create a special coro because we want to cede,
		521	# to reduce pressure on the coro pool (because most callbacks
		522	# return immediately and can be reused) and because we cannot cede
		523	# inside an event callback.
		524	our $unblock_scheduler = async {
		525	while () {
		526	while (my $cb = pop @unblock_queue) {
		527	# this is an inlined copy of async_pool
		528	my $coro = (pop @pool or new Coro \&pool_handler);
		529
		530	$coro->{_invoke} = $cb;
		531	$coro->ready;
		532	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		533	}
		534	schedule; # sleep well
		535	}
119	};	536	};
120		537
		538	sub unblock_sub(&) {
		539	my $cb = shift;
		540
		541	sub {
		542	unshift @unblock_queue, [$cb, @_];
		543	$unblock_scheduler->ready;
		544	}
		545	}
		546
		547	=back
		548
		549	=cut
		550
121	1;	551	1;
122		552
123	=back	553	=head1 BUGS/LIMITATIONS
124		554
125	=head1 BUGS	555	- you must make very sure that no coro is still active on global
		556	destruction. very bad things might happen otherwise (usually segfaults).
126		557
127	This module has not yet been extensively tested.	558	- this module is not thread-safe. You should only ever use this module
		559	from the same thread (this requirement might be losened in the future
		560	to allow per-thread schedulers, but Coro::State does not yet allow
		561	this).
128		562
129	=head1 SEE ALSO	563	=head1 SEE ALSO
130		564
131	L<Coro::Process>, L<Coro::Signal>.	565	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		566
		567	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		568
		569	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		570
		571	Embedding: L<Coro:MakeMaker>
132		572
133	=head1 AUTHOR	573	=head1 AUTHOR
134		574
135	Marc Lehmann <pcg@goof.com>	575	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	576	http://home.schmorp.de/
137		577
138	=cut	578	=cut
139		579

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Comparing Coro/Coro.pm (file contents): Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs. Revision 1.105 by root, Fri Jan 5 16:55:01 2007 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs.
Revision 1.105 by root, Fri Jan 5 16:55:01 2007 UTC