[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 1.108 by root, Fri Jan 5 20:00:49 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
		216	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		217	will not work in the expected way, unless you call terminate or cancel,
		218	which somehow defeats the purpose of pooling.
		219
		220	The priority will be reset to C<0> after each job, otherwise the coroutine
		221	will be re-used "as-is".
		222
		223	The pool size is limited to 8 idle coroutines (this can be adjusted by
		224	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		225	required.
		226
		227	If you are concerned about pooled coroutines growing a lot because a
		228	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
		229	terminate }> once per second or so to slowly replenish the pool.
		230
		231	=cut
		232
		233	our $POOL_SIZE = 8;
		234	our @pool;
		235
		236	sub pool_handler {
		237	while () {
		238	my ($cb, @arg) = @{ delete $current->{_invoke} };
		239
		240	eval {
		241	$cb->(@arg);
		242	};
		243	warn $@ if $@;
		244
		245	last if @pool >= $POOL_SIZE;
		246	push @pool, $current;
		247
		248	$current->prio (0);
		249	schedule;
		250	}
		251	}
		252
		253	sub async_pool(&@) {
		254	# this is also inlined into the unlock_scheduler
		255	my $coro = (pop @pool or new Coro \&pool_handler);
		256
		257	$coro->{_invoke} = [@_];
		258	$coro->ready;
		259
		260	$coro
		261	}
		262
		263	=item schedule
		264
		265	Calls the scheduler. Please note that the current coroutine will not be put
		266	into the ready queue, so calling this function usually means you will
		267	never be called again unless something else (e.g. an event handler) calls
		268	ready.
		269
		270	The canonical way to wait on external events is this:
		271
		272	{
		273	# remember current coroutine
		274	my $current = $Coro::current;
		275
		276	# register a hypothetical event handler
		277	on_event_invoke sub {
		278	# wake up sleeping coroutine
		279	$current->ready;
		280	undef $current;
		281	};
		282
		283	# call schedule until event occured.
		284	# in case we are woken up for other reasons
		285	# (current still defined), loop.
		286	Coro::schedule while $current;
		287	}
		288
		289	=item cede
		290
		291	"Cede" to other coroutines. This function puts the current coroutine into the
		292	ready queue and calls C<schedule>, which has the effect of giving up the
		293	current "timeslice" to other coroutines of the same or higher priority.
		294
		295	Returns true if at least one coroutine switch has happened.
		296
		297	=item Coro::cede_notself
		298
		299	Works like cede, but is not exported by default and will cede to any
		300	coroutine, regardless of priority, once.
		301
		302	Returns true if at least one coroutine switch has happened.
		303
		304	=item terminate [arg...]
		305
		306	Terminates the current coroutine with the given status values (see L<cancel>).
		307
		308	=cut
		309
		310	sub terminate {
		311	$current->cancel (@_);
		312	}
		313
		314	=back
		315
		316	# dynamic methods
		317
		318	=head2 COROUTINE METHODS
		319
		320	These are the methods you can call on coroutine objects.
		321
		322	=over 4
		323
		324	=item new Coro \&sub [, @args...]
		325
		326	Create a new coroutine and return it. When the sub returns the coroutine
		327	automatically terminates as if C<terminate> with the returned values were
		328	called. To make the coroutine run you must first put it into the ready queue
		329	by calling the ready method.
		330
		331	Calling C<exit> in a coroutine will not work correctly, so do not do that.
		332
		333	=cut
		334
		335	sub _run_coro {
		336	terminate &{+shift};
		337	}
59		338
60	sub new {	339	sub new {
61	my $class = $_[0];	340	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		341
75	=item $prev->transfer($next)	342	$class->SUPER::new (\&_run_coro, @_)
		343	}
76		344
77	Save the state of the current subroutine in C<$prev> and switch to the	345	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		346
80	The "state" of a subroutine only ever includes scope, i.e. lexical	347	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	348	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	349	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		350
88	The easiest way to do this is to create your own scheduling primitive like this:	351	=item $is_ready = $coroutine->is_ready
89		352
90	sub schedule {	353	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	354
92	$old->transfer($new);	355	=item $coroutine->cancel (arg...)
		356
		357	Terminates the given coroutine and makes it return the given arguments as
		358	status (default: the empty list). Never returns if the coroutine is the
		359	current coroutine.
		360
		361	=cut
		362
		363	sub cancel {
		364	my $self = shift;
		365	$self->{status} = [@_];
		366
		367	if ($current == $self) {
		368	push @destroy, $self;
		369	$manager->ready;
		370	&schedule while 1;
		371	} else {
		372	$self->_cancel;
93	}	373	}
94
95	=cut
96
97	# I call the _transfer function from a perl function
98	# because that way perl saves all important things on
99	# the stack. Actually, I'd do it from within XS, but
100	# I couldn't get it to work.
101	sub transfer {
102	_transfer($_[0], $_[1]);
103	}	374	}
104		375
105	=item $error, $error_msg, $error_coro	376	=item $coroutine->join
106		377
107	This coroutine will be called on fatal errors. C<$error_msg> and	378	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	379	C<terminate> or C<cancel> functions. C<join> can be called multiple times
109	(NOT an object) respectively. This API might change.	380	from multiple coroutine.
110		381
111	=cut	382	=cut
112		383
113	$error_msg =	384	sub join {
114	$error_coro = undef;	385	my $self = shift;
115		386
116	$error = _newprocess {	387	unless ($self->{status}) {
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	388	my $current = $current;
118	exit 50;	389
		390	push @{$self->{destroy_cb}}, sub {
		391	$current->ready;
		392	undef $current;
		393	};
		394
		395	&schedule while $current;
		396	}
		397
		398	wantarray ? @{$self->{status}} : $self->{status}[0];
		399	}
		400
		401	=item $coroutine->on_destroy (\&cb)
		402
		403	Registers a callback that is called when this coroutine gets destroyed,
		404	but before it is joined. The callback gets passed the terminate arguments,
		405	if any.
		406
		407	=cut
		408
		409	sub on_destroy {
		410	my ($self, $cb) = @_;
		411
		412	push @{ $self->{destroy_cb} }, $cb;
		413	}
		414
		415	=item $oldprio = $coroutine->prio ($newprio)
		416
		417	Sets (or gets, if the argument is missing) the priority of the
		418	coroutine. Higher priority coroutines get run before lower priority
		419	coroutines. Priorities are small signed integers (currently -4 .. +3),
		420	that you can refer to using PRIO_xxx constants (use the import tag :prio
		421	to get then):
		422
		423	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		424	3 > 1 > 0 > -1 > -3 > -4
		425
		426	# set priority to HIGH
		427	current->prio(PRIO_HIGH);
		428
		429	The idle coroutine ($Coro::idle) always has a lower priority than any
		430	existing coroutine.
		431
		432	Changing the priority of the current coroutine will take effect immediately,
		433	but changing the priority of coroutines in the ready queue (but not
		434	running) will only take effect after the next schedule (of that
		435	coroutine). This is a bug that will be fixed in some future version.
		436
		437	=item $newprio = $coroutine->nice ($change)
		438
		439	Similar to C<prio>, but subtract the given value from the priority (i.e.
		440	higher values mean lower priority, just as in unix).
		441
		442	=item $olddesc = $coroutine->desc ($newdesc)
		443
		444	Sets (or gets in case the argument is missing) the description for this
		445	coroutine. This is just a free-form string you can associate with a coroutine.
		446
		447	=cut
		448
		449	sub desc {
		450	my $old = $_[0]{desc};
		451	$_[0]{desc} = $_[1] if @_ > 1;
		452	$old;
		453	}
		454
		455	=back
		456
		457	=head2 GLOBAL FUNCTIONS
		458
		459	=over 4
		460
		461	=item Coro::nready
		462
		463	Returns the number of coroutines that are currently in the ready state,
		464	i.e. that can be swicthed to. The value C<0> means that the only runnable
		465	coroutine is the currently running one, so C<cede> would have no effect,
		466	and C<schedule> would cause a deadlock unless there is an idle handler
		467	that wakes up some coroutines.
		468
		469	=item my $guard = Coro::guard { ... }
		470
		471	This creates and returns a guard object. Nothing happens until the objetc
		472	gets destroyed, in which case the codeblock given as argument will be
		473	executed. This is useful to free locks or other resources in case of a
		474	runtime error or when the coroutine gets canceled, as in both cases the
		475	guard block will be executed. The guard object supports only one method,
		476	C<< ->cancel >>, which will keep the codeblock from being executed.
		477
		478	Example: set some flag and clear it again when the coroutine gets canceled
		479	or the function returns:
		480
		481	sub do_something {
		482	my $guard = Coro::guard { $busy = 0 };
		483	$busy = 1;
		484
		485	# do something that requires $busy to be true
		486	}
		487
		488	=cut
		489
		490	sub guard(&) {
		491	bless \(my $cb = $_[0]), "Coro::guard"
		492	}
		493
		494	sub Coro::guard::cancel {
		495	${$_[0]} = sub { };
		496	}
		497
		498	sub Coro::guard::DESTROY {
		499	${$_[0]}->();
		500	}
		501
		502
		503	=item unblock_sub { ... }
		504
		505	This utility function takes a BLOCK or code reference and "unblocks" it,
		506	returning the new coderef. This means that the new coderef will return
		507	immediately without blocking, returning nothing, while the original code
		508	ref will be called (with parameters) from within its own coroutine.
		509
		510	The reason this fucntion exists is that many event libraries (such as the
		511	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		512	of thread-safety). This means you must not block within event callbacks,
		513	otherwise you might suffer from crashes or worse.
		514
		515	This function allows your callbacks to block by executing them in another
		516	coroutine where it is safe to block. One example where blocking is handy
		517	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		518	disk.
		519
		520	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		521	creating event callbacks that want to block.
		522
		523	=cut
		524
		525	our @unblock_queue;
		526
		527	# we create a special coro because we want to cede,
		528	# to reduce pressure on the coro pool (because most callbacks
		529	# return immediately and can be reused) and because we cannot cede
		530	# inside an event callback.
		531	our $unblock_scheduler = async {
		532	while () {
		533	while (my $cb = pop @unblock_queue) {
		534	# this is an inlined copy of async_pool
		535	my $coro = (pop @pool or new Coro \&pool_handler);
		536
		537	$coro->{_invoke} = $cb;
		538	$coro->ready;
		539	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		540	}
		541	schedule; # sleep well
		542	}
119	};	543	};
120		544
		545	sub unblock_sub(&) {
		546	my $cb = shift;
		547
		548	sub {
		549	unshift @unblock_queue, [$cb, @_];
		550	$unblock_scheduler->ready;
		551	}
		552	}
		553
		554	=back
		555
		556	=cut
		557
121	1;	558	1;
122		559
123	=back	560	=head1 BUGS/LIMITATIONS
124		561
125	=head1 BUGS	562	- you must make very sure that no coro is still active on global
		563	destruction. very bad things might happen otherwise (usually segfaults).
126		564
127	This module has not yet been extensively tested.	565	- this module is not thread-safe. You should only ever use this module
		566	from the same thread (this requirement might be losened in the future
		567	to allow per-thread schedulers, but Coro::State does not yet allow
		568	this).
128		569
129	=head1 SEE ALSO	570	=head1 SEE ALSO
130		571
131	L<Coro::Process>, L<Coro::Signal>.	572	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		573
		574	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		575
		576	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		577
		578	Embedding: L<Coro:MakeMaker>
132		579
133	=head1 AUTHOR	580	=head1 AUTHOR
134		581
135	Marc Lehmann <pcg@goof.com>	582	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	583	http://home.schmorp.de/
137		584
138	=cut	585	=cut
139		586

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing Coro/Coro.pm (file contents): Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs. Revision 1.108 by root, Fri Jan 5 20:00:49 2007 UTC

Diff Legend

Comparing Coro/Coro.pm (file contents):
Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs.
Revision 1.108 by root, Fri Jan 5 20:00:49 2007 UTC