[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 1.104 by root, Thu Jan 4 23:49:27 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 $VERSION = '3.3';
		56
		57	our @EXPORT = qw(async cede schedule terminate current unblock_sub);
		58	our %EXPORT_TAGS = (
		59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		60	);
		61	our @EXPORT_OK = (@{$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 schedule
		209
		210	Calls the scheduler. Please note that the current coroutine will not be put
		211	into the ready queue, so calling this function usually means you will
		212	never be called again unless something else (e.g. an event handler) calls
		213	ready.
		214
		215	The canonical way to wait on external events is this:
		216
		217	{
		218	# remember current coroutine
		219	my $current = $Coro::current;
		220
		221	# register a hypothetical event handler
		222	on_event_invoke sub {
		223	# wake up sleeping coroutine
		224	$current->ready;
		225	undef $current;
		226	};
		227
		228	# call schedule until event occured.
		229	# in case we are woken up for other reasons
		230	# (current still defined), loop.
		231	Coro::schedule while $current;
		232	}
		233
		234	=item cede
		235
		236	"Cede" to other coroutines. This function puts the current coroutine into the
		237	ready queue and calls C<schedule>, which has the effect of giving up the
		238	current "timeslice" to other coroutines of the same or higher priority.
		239
		240	=item Coro::cede_notself
		241
		242	Works like cede, but is not exported by default and will cede to any
		243	coroutine, regardless of priority, once.
		244
		245	=item terminate [arg...]
		246
		247	Terminates the current coroutine with the given status values (see L<cancel>).
		248
		249	=cut
		250
		251	sub terminate {
		252	$current->cancel (@_);
		253	}
		254
		255	=back
		256
		257	# dynamic methods
		258
		259	=head2 COROUTINE METHODS
		260
		261	These are the methods you can call on coroutine objects.
		262
		263	=over 4
		264
		265	=item new Coro \&sub [, @args...]
		266
		267	Create a new coroutine and return it. When the sub returns the coroutine
		268	automatically terminates as if C<terminate> with the returned values were
		269	called. To make the coroutine run you must first put it into the ready queue
		270	by calling the ready method.
		271
		272	Calling C<exit> in a coroutine will not work correctly, so do not do that.
		273
		274	=cut
		275
		276	sub _run_coro {
		277	terminate &{+shift};
		278	}
59		279
60	sub new {	280	sub new {
61	my $class = $_[0];	281	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		282
75	=item $prev->transfer($next)	283	$class->SUPER::new (\&_run_coro, @_)
		284	}
76		285
77	Save the state of the current subroutine in C<$prev> and switch to the	286	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		287
80	The "state" of a subroutine only ever includes scope, i.e. lexical	288	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	289	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	290	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		291
88	The easiest way to do this is to create your own scheduling primitive like this:	292	=item $is_ready = $coroutine->is_ready
89		293
90	sub schedule {	294	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	295
92	$old->transfer($new);	296	=item $coroutine->cancel (arg...)
		297
		298	Terminates the given coroutine and makes it return the given arguments as
		299	status (default: the empty list). Never returns if the coroutine is the
		300	current coroutine.
		301
		302	=cut
		303
		304	sub cancel {
		305	my $self = shift;
		306	$self->{status} = [@_];
		307
		308	if ($current == $self) {
		309	push @destroy, $self;
		310	$manager->ready;
		311	&schedule while 1;
		312	} else {
		313	$self->_cancel;
93	}	314	}
94
95	=cut
96
97	# I call the _transfer function from a perl function
98	# because that way perl saves all important things on
99	# the stack. Actually, I'd do it from within XS, but
100	# I couldn't get it to work.
101	sub transfer {
102	_transfer($_[0], $_[1]);
103	}	315	}
104		316
105	=item $error, $error_msg, $error_coro	317	=item $coroutine->join
106		318
107	This coroutine will be called on fatal errors. C<$error_msg> and	319	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	320	C<terminate> or C<cancel> functions. C<join> can be called multiple times
109	(NOT an object) respectively. This API might change.	321	from multiple coroutine.
110		322
111	=cut	323	=cut
112		324
113	$error_msg =	325	sub join {
114	$error_coro = undef;	326	my $self = shift;
115		327
116	$error = _newprocess {	328	unless ($self->{status}) {
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	329	my $current = $current;
118	exit 50;	330
		331	push @{$self->{destroy_cb}}, sub {
		332	$current->ready;
		333	undef $current;
		334	};
		335
		336	&schedule while $current;
		337	}
		338
		339	wantarray ? @{$self->{status}} : $self->{status}[0];
		340	}
		341
		342	=item $coroutine->on_destroy (\&cb)
		343
		344	Registers a callback that is called when this coroutine gets destroyed,
		345	but before it is joined. The callback gets passed the terminate arguments,
		346	if any.
		347
		348	=cut
		349
		350	sub on_destroy {
		351	my ($self, $cb) = @_;
		352
		353	push @{ $self->{destroy_cb} }, $cb;
		354	}
		355
		356	=item $oldprio = $coroutine->prio ($newprio)
		357
		358	Sets (or gets, if the argument is missing) the priority of the
		359	coroutine. Higher priority coroutines get run before lower priority
		360	coroutines. Priorities are small signed integers (currently -4 .. +3),
		361	that you can refer to using PRIO_xxx constants (use the import tag :prio
		362	to get then):
		363
		364	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		365	3 > 1 > 0 > -1 > -3 > -4
		366
		367	# set priority to HIGH
		368	current->prio(PRIO_HIGH);
		369
		370	The idle coroutine ($Coro::idle) always has a lower priority than any
		371	existing coroutine.
		372
		373	Changing the priority of the current coroutine will take effect immediately,
		374	but changing the priority of coroutines in the ready queue (but not
		375	running) will only take effect after the next schedule (of that
		376	coroutine). This is a bug that will be fixed in some future version.
		377
		378	=item $newprio = $coroutine->nice ($change)
		379
		380	Similar to C<prio>, but subtract the given value from the priority (i.e.
		381	higher values mean lower priority, just as in unix).
		382
		383	=item $olddesc = $coroutine->desc ($newdesc)
		384
		385	Sets (or gets in case the argument is missing) the description for this
		386	coroutine. This is just a free-form string you can associate with a coroutine.
		387
		388	=cut
		389
		390	sub desc {
		391	my $old = $_[0]{desc};
		392	$_[0]{desc} = $_[1] if @_ > 1;
		393	$old;
		394	}
		395
		396	=back
		397
		398	=head2 GLOBAL FUNCTIONS
		399
		400	=over 4
		401
		402	=item Coro::nready
		403
		404	Returns the number of coroutines that are currently in the ready state,
		405	i.e. that can be swicthed to. The value C<0> means that the only runnable
		406	coroutine is the currently running one, so C<cede> would have no effect,
		407	and C<schedule> would cause a deadlock unless there is an idle handler
		408	that wakes up some coroutines.
		409
		410	=item my $guard = Coro::guard { ... }
		411
		412	This creates and returns a guard object. Nothing happens until the objetc
		413	gets destroyed, in which case the codeblock given as argument will be
		414	executed. This is useful to free locks or other resources in case of a
		415	runtime error or when the coroutine gets canceled, as in both cases the
		416	guard block will be executed. The guard object supports only one method,
		417	C<< ->cancel >>, which will keep the codeblock from being executed.
		418
		419	Example: set some flag and clear it again when the coroutine gets canceled
		420	or the function returns:
		421
		422	sub do_something {
		423	my $guard = Coro::guard { $busy = 0 };
		424	$busy = 1;
		425
		426	# do something that requires $busy to be true
		427	}
		428
		429	=cut
		430
		431	sub guard(&) {
		432	bless \(my $cb = $_[0]), "Coro::guard"
		433	}
		434
		435	sub Coro::guard::cancel {
		436	${$_[0]} = sub { };
		437	}
		438
		439	sub Coro::guard::DESTROY {
		440	${$_[0]}->();
		441	}
		442
		443
		444	=item unblock_sub { ... }
		445
		446	This utility function takes a BLOCK or code reference and "unblocks" it,
		447	returning the new coderef. This means that the new coderef will return
		448	immediately without blocking, returning nothing, while the original code
		449	ref will be called (with parameters) from within its own coroutine.
		450
		451	The reason this fucntion exists is that many event libraries (such as the
		452	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		453	of thread-safety). This means you must not block within event callbacks,
		454	otherwise you might suffer from crashes or worse.
		455
		456	This function allows your callbacks to block by executing them in another
		457	coroutine where it is safe to block. One example where blocking is handy
		458	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		459	disk.
		460
		461	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		462	creating event callbacks that want to block.
		463
		464	=cut
		465
		466	our @unblock_pool;
		467	our @unblock_queue;
		468	our $UNBLOCK_POOL_SIZE = 2;
		469
		470	sub unblock_handler_ {
		471	while () {
		472	my ($cb, @arg) = @{ delete $Coro::current->{arg} };
		473	$cb->(@arg);
		474
		475	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
		476	push @unblock_pool, $Coro::current;
		477	schedule;
		478	}
		479	}
		480
		481	our $unblock_scheduler = async {
		482	while () {
		483	while (my $cb = pop @unblock_queue) {
		484	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);
		485	$handler->{arg} = $cb;
		486	$handler->ready;
		487	cede;
		488	}
		489
		490	schedule;
		491	}
119	};	492	};
120		493
		494	sub unblock_sub(&) {
		495	my $cb = shift;
		496
		497	sub {
		498	push @unblock_queue, [$cb, @_];
		499	$unblock_scheduler->ready;
		500	}
		501	}
		502
		503	=back
		504
		505	=cut
		506
121	1;	507	1;
122		508
123	=back	509	=head1 BUGS/LIMITATIONS
124		510
125	=head1 BUGS	511	- you must make very sure that no coro is still active on global
		512	destruction. very bad things might happen otherwise (usually segfaults).
126		513
127	This module has not yet been extensively tested.	514	- this module is not thread-safe. You should only ever use this module
		515	from the same thread (this requirement might be losened in the future
		516	to allow per-thread schedulers, but Coro::State does not yet allow
		517	this).
128		518
129	=head1 SEE ALSO	519	=head1 SEE ALSO
130		520
131	L<Coro::Process>, L<Coro::Signal>.	521	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		522
		523	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		524
		525	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		526
		527	Embedding: L<Coro:MakeMaker>
132		528
133	=head1 AUTHOR	529	=head1 AUTHOR
134		530
135	Marc Lehmann <pcg@goof.com>	531	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	532	http://home.schmorp.de/
137		533
138	=cut	534	=cut
139		535

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 1.104 by root, Thu Jan 4 23:49:27 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 1.104 by root, Thu Jan 4 23:49:27 2007 UTC