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

Comparing Coro/Coro.pm (file contents):
Revision 1.5 by root, Tue Jul 10 01:43:21 2001 UTC vs.
Revision 1.121 by root, Fri Apr 13 12:56:55 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 use din this module also
27	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.
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 $VERSION = '3.56';
		56
		57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		58	our %EXPORT_TAGS = (
		59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		60	);
		61	our @EXPORT_OK = (@{$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 = 0.03;
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 essentiel 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 try to do the same as calling exit
		191	outside the coroutine, but this is experimental. It is best not to rely on
		192	exit doing any cleanups or even not crashing.
		193
		194	When the coroutine dies, the program will exit, just as in the main
		195	program.
		196
		197	# create a new coroutine that just prints its arguments
		198	async {
		199	print "@_\n";
		200	} 1,2,3,4;
		201
83	=cut	202	=cut
		203
		204	sub async(&@) {
		205	my $coro = new Coro @_;
		206	$coro->ready;
		207	$coro
		208	}
		209
		210	=item async_pool { ... } [@args...]
		211
		212	Similar to C<async>, but uses a coroutine pool, so you should not call
		213	terminate or join (although you are allowed to), and you get a coroutine
		214	that might have executed other code already (which can be good or bad :).
		215
		216	Also, the block is executed in an C<eval> context and a warning will be
		217	issued in case of an exception instead of terminating the program, as
		218	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		219	will not work in the expected way, unless you call terminate or cancel,
		220	which somehow defeats the purpose of pooling.
		221
		222	The priority will be reset to C<0> after each job, otherwise the coroutine
		223	will be re-used "as-is".
		224
		225	The pool size is limited to 8 idle coroutines (this can be adjusted by
		226	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		227	required.
		228
		229	If you are concerned about pooled coroutines growing a lot because a
		230	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
		231	terminate }> once per second or so to slowly replenish the pool.
		232
		233	=cut
		234
		235	our $POOL_SIZE = 8;
		236	our @pool;
		237
		238	sub pool_handler {
		239	while () {
		240	eval {
		241	my ($cb, @arg) = @{ delete $current->{_invoke} or return };
		242	$cb->(@arg);
		243	};
		244	warn $@ if $@;
		245
		246	last if @pool >= $POOL_SIZE;
		247	push @pool, $current;
		248
		249	$current->save (Coro::State::SAVE_DEF);
		250	$current->prio (0);
		251	schedule;
		252	}
		253	}
		254
		255	sub async_pool(&@) {
		256	# this is also inlined into the unlock_scheduler
		257	my $coro = (pop @pool or new Coro \&pool_handler);
		258
		259	$coro->{_invoke} = [@_];
		260	$coro->ready;
		261
		262	$coro
		263	}
		264
		265	=item schedule
		266
		267	Calls the scheduler. Please note that the current coroutine will not be put
		268	into the ready queue, so calling this function usually means you will
		269	never be called again unless something else (e.g. an event handler) calls
		270	ready.
		271
		272	The canonical way to wait on external events is this:
		273
		274	{
		275	# remember current coroutine
		276	my $current = $Coro::current;
		277
		278	# register a hypothetical event handler
		279	on_event_invoke sub {
		280	# wake up sleeping coroutine
		281	$current->ready;
		282	undef $current;
		283	};
		284
		285	# call schedule until event occured.
		286	# in case we are woken up for other reasons
		287	# (current still defined), loop.
		288	Coro::schedule while $current;
		289	}
		290
		291	=item cede
		292
		293	"Cede" to other coroutines. This function puts the current coroutine into the
		294	ready queue and calls C<schedule>, which has the effect of giving up the
		295	current "timeslice" to other coroutines of the same or higher priority.
		296
		297	Returns true if at least one coroutine switch has happened.
		298
		299	=item Coro::cede_notself
		300
		301	Works like cede, but is not exported by default and will cede to any
		302	coroutine, regardless of priority, once.
		303
		304	Returns true if at least one coroutine switch has happened.
		305
		306	=item terminate [arg...]
		307
		308	Terminates the current coroutine with the given status values (see L<cancel>).
		309
		310	=cut
		311
		312	sub terminate {
		313	$current->cancel (@_);
		314	}
		315
		316	=back
		317
		318	# dynamic methods
		319
		320	=head2 COROUTINE METHODS
		321
		322	These are the methods you can call on coroutine objects.
		323
		324	=over 4
		325
		326	=item new Coro \&sub [, @args...]
		327
		328	Create a new coroutine and return it. When the sub returns the coroutine
		329	automatically terminates as if C<terminate> with the returned values were
		330	called. To make the coroutine run you must first put it into the ready queue
		331	by calling the ready method.
		332
		333	See C<async> for additional discussion.
		334
		335	=cut
		336
		337	sub _run_coro {
		338	terminate &{+shift};
		339	}
84		340
85	sub new {	341	sub new {
86	my $class = $_[0];	342	my $class = shift;
87	my $proc = $_[1];	343
88	bless _newprocess {	344	$class->SUPER::new (\&_run_coro, @_)
89	do {	345	}
90	eval { &$proc->resume };	346
91	if ($@) {	347	=item $success = $coroutine->ready
92	($error_msg, $error_coro) = ($@, $current);	348
93	$error->resume;	349	Put the given coroutine into the ready queue (according to it's priority)
		350	and return true. If the coroutine is already in the ready queue, do nothing
		351	and return false.
		352
		353	=item $is_ready = $coroutine->is_ready
		354
		355	Return wether the coroutine is currently the ready queue or not,
		356
		357	=item $coroutine->cancel (arg...)
		358
		359	Terminates the given coroutine and makes it return the given arguments as
		360	status (default: the empty list). Never returns if the coroutine is the
		361	current coroutine.
		362
		363	=cut
		364
		365	sub cancel {
		366	my $self = shift;
		367	$self->{status} = [@_];
		368
		369	if ($current == $self) {
		370	push @destroy, $self;
		371	$manager->ready;
		372	&schedule while 1;
		373	} else {
		374	$self->_cancel;
		375	}
		376	}
		377
		378	=item $coroutine->join
		379
		380	Wait until the coroutine terminates and return any values given to the
		381	C<terminate> or C<cancel> functions. C<join> can be called multiple times
		382	from multiple coroutine.
		383
		384	=cut
		385
		386	sub join {
		387	my $self = shift;
		388
		389	unless ($self->{status}) {
		390	my $current = $current;
		391
		392	push @{$self->{destroy_cb}}, sub {
		393	$current->ready;
		394	undef $current;
		395	};
		396
		397	&schedule while $current;
		398	}
		399
		400	wantarray ? @{$self->{status}} : $self->{status}[0];
		401	}
		402
		403	=item $coroutine->on_destroy (\&cb)
		404
		405	Registers a callback that is called when this coroutine gets destroyed,
		406	but before it is joined. The callback gets passed the terminate arguments,
		407	if any.
		408
		409	=cut
		410
		411	sub on_destroy {
		412	my ($self, $cb) = @_;
		413
		414	push @{ $self->{destroy_cb} }, $cb;
		415	}
		416
		417	=item $oldprio = $coroutine->prio ($newprio)
		418
		419	Sets (or gets, if the argument is missing) the priority of the
		420	coroutine. Higher priority coroutines get run before lower priority
		421	coroutines. Priorities are small signed integers (currently -4 .. +3),
		422	that you can refer to using PRIO_xxx constants (use the import tag :prio
		423	to get then):
		424
		425	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		426	3 > 1 > 0 > -1 > -3 > -4
		427
		428	# set priority to HIGH
		429	current->prio(PRIO_HIGH);
		430
		431	The idle coroutine ($Coro::idle) always has a lower priority than any
		432	existing coroutine.
		433
		434	Changing the priority of the current coroutine will take effect immediately,
		435	but changing the priority of coroutines in the ready queue (but not
		436	running) will only take effect after the next schedule (of that
		437	coroutine). This is a bug that will be fixed in some future version.
		438
		439	=item $newprio = $coroutine->nice ($change)
		440
		441	Similar to C<prio>, but subtract the given value from the priority (i.e.
		442	higher values mean lower priority, just as in unix).
		443
		444	=item $olddesc = $coroutine->desc ($newdesc)
		445
		446	Sets (or gets in case the argument is missing) the description for this
		447	coroutine. This is just a free-form string you can associate with a coroutine.
		448
		449	=cut
		450
		451	sub desc {
		452	my $old = $_[0]{desc};
		453	$_[0]{desc} = $_[1] if @_ > 1;
		454	$old;
		455	}
		456
		457	=back
		458
		459	=head2 GLOBAL FUNCTIONS
		460
		461	=over 4
		462
		463	=item Coro::nready
		464
		465	Returns the number of coroutines that are currently in the ready state,
		466	i.e. that can be swicthed to. The value C<0> means that the only runnable
		467	coroutine is the currently running one, so C<cede> would have no effect,
		468	and C<schedule> would cause a deadlock unless there is an idle handler
		469	that wakes up some coroutines.
		470
		471	=item my $guard = Coro::guard { ... }
		472
		473	This creates and returns a guard object. Nothing happens until the object
		474	gets destroyed, in which case the codeblock given as argument will be
		475	executed. This is useful to free locks or other resources in case of a
		476	runtime error or when the coroutine gets canceled, as in both cases the
		477	guard block will be executed. The guard object supports only one method,
		478	C<< ->cancel >>, which will keep the codeblock from being executed.
		479
		480	Example: set some flag and clear it again when the coroutine gets canceled
		481	or the function returns:
		482
		483	sub do_something {
		484	my $guard = Coro::guard { $busy = 0 };
		485	$busy = 1;
		486
		487	# do something that requires $busy to be true
		488	}
		489
		490	=cut
		491
		492	sub guard(&) {
		493	bless \(my $cb = $_[0]), "Coro::guard"
		494	}
		495
		496	sub Coro::guard::cancel {
		497	${$_[0]} = sub { };
		498	}
		499
		500	sub Coro::guard::DESTROY {
		501	${$_[0]}->();
		502	}
		503
		504
		505	=item unblock_sub { ... }
		506
		507	This utility function takes a BLOCK or code reference and "unblocks" it,
		508	returning the new coderef. This means that the new coderef will return
		509	immediately without blocking, returning nothing, while the original code
		510	ref will be called (with parameters) from within its own coroutine.
		511
		512	The reason this fucntion exists is that many event libraries (such as the
		513	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		514	of thread-safety). This means you must not block within event callbacks,
		515	otherwise you might suffer from crashes or worse.
		516
		517	This function allows your callbacks to block by executing them in another
		518	coroutine where it is safe to block. One example where blocking is handy
		519	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		520	disk.
		521
		522	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		523	creating event callbacks that want to block.
		524
		525	=cut
		526
		527	our @unblock_queue;
		528
		529	# we create a special coro because we want to cede,
		530	# to reduce pressure on the coro pool (because most callbacks
		531	# return immediately and can be reused) and because we cannot cede
		532	# inside an event callback.
		533	our $unblock_scheduler = async {
		534	while () {
		535	while (my $cb = pop @unblock_queue) {
		536	# this is an inlined copy of async_pool
		537	my $coro = (pop @pool or new Coro \&pool_handler);
		538
		539	$coro->{_invoke} = $cb;
		540	$coro->ready;
		541	cede; # for short-lived callbacks, this reduces pressure on the coro pool
94	}	542	}
95	} while (1);	543	schedule; # sleep well
96	}, $class;	544	}
97	}	545	};
98		546
99	=item $coro->resume	547	sub unblock_sub(&) {
		548	my $cb = shift;
100		549
101	Resume execution at the given coroutine.	550	sub {
102		551	unshift @unblock_queue, [$cb, @_];
103	=cut	552	$unblock_scheduler->ready;
104		553	}
105	my $prev;
106
107	# I call the _transfer function from a pelr function
108	# because that way perl saves all important things on
109	# the stack.
110	sub resume {
111	$prev = $current; $current = $_[0];
112	_transfer($prev, $current);
113	}	554	}
		555
		556	=back
		557
		558	=cut
114		559
115	1;	560	1;
116		561
117	=back	562	=head1 BUGS/LIMITATIONS
118		563
119	=head1 BUGS	564	- you must make very sure that no coro is still active on global
		565	destruction. very bad things might happen otherwise (usually segfaults).
120		566
121	This module has not yet been extensively tested.	567	- this module is not thread-safe. You should only ever use this module
		568	from the same thread (this requirement might be losened in the future
		569	to allow per-thread schedulers, but Coro::State does not yet allow
		570	this).
122		571
123	=head1 SEE ALSO	572	=head1 SEE ALSO
124		573
125	L<Coro::Process>, L<Coro::Signal>.	574	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		575
		576	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		577
		578	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		579
		580	Embedding: L<Coro:MakeMaker>
126		581
127	=head1 AUTHOR	582	=head1 AUTHOR
128		583
129	Marc Lehmann <pcg@goof.com>	584	Marc Lehmann <schmorp@schmorp.de>
130	http://www.goof.com/pcg/marc/	585	http://home.schmorp.de/
131		586
132	=cut	587	=cut
133		588

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Comparing Coro/Coro.pm (file contents): Revision 1.5 by root, Tue Jul 10 01:43:21 2001 UTC vs. Revision 1.121 by root, Fri Apr 13 12:56:55 2007 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.5 by root, Tue Jul 10 01:43:21 2001 UTC vs.
Revision 1.121 by root, Fri Apr 13 12:56:55 2007 UTC