[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 1.102 by root, Fri Dec 29 11:37:49 2006 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	# this coroutine is necessary because a coroutine
		147	# cannot destroy itself.
		148	my @destroy;
		149	my $manager; $manager = new Coro sub {
		150	while () {
		151	# by overwriting the state object with the manager we destroy it
		152	# while still being able to schedule this coroutine (in case it has
		153	# been readied multiple times. this is harmless since the manager
		154	# can be called as many times as neccessary and will always
		155	# remove itself from the runqueue
		156	while (@destroy) {
		157	my $coro = pop @destroy;
49		158
50	Create a new coroutine and return it. The first C<transfer> call to this	159	$coro->{status} \|\|= [];
51	coroutine will start execution at the given coderef. If, the subroutine
52	returns it will be executed again.
53		160
54	If the coderef is omitted this function will create a new "empty"	161	$_->ready for @{(delete $coro->{join} ) \|\| []};
55	coroutine, i.e. a coroutine that cannot be transfered to but can be used	162	$_->(@{$coro->{status}}) for @{(delete $coro->{destroy_cb}) \|\| []};
56	to save the current coroutine in.
57		163
		164	# the next line destroys the coro state, but keeps the
		165	# coroutine itself intact (we basically make it a zombie
		166	# coroutine that always runs the manager thread, so it's possible
		167	# to transfer() to this coroutine).
		168	$coro->_clone_state_from ($manager);
		169	}
		170	&schedule;
		171	}
		172	};
		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 $pid = new Coro @_;
		204	$pid->ready;
		205	$pid
		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).
		300
		301	=cut
		302
		303	sub cancel {
		304	my $self = shift;
		305	$self->{status} = [@_];
		306	push @destroy, $self;
		307	$manager->ready;
		308	&schedule if $current == $self;
		309	}
		310
		311	=item $coroutine->join
		312
		313	Wait until the coroutine terminates and return any values given to the
		314	C<terminate> or C<cancel> functions. C<join> can be called multiple times
		315	from multiple coroutine.
		316
		317	=cut
		318
		319	sub join {
		320	my $self = shift;
		321	unless ($self->{status}) {
		322	push @{$self->{join}}, $current;
		323	&schedule;
93	}	324	}
94		325	wantarray ? @{$self->{status}} : $self->{status}[0];
95	=cut
96
97	# I call the _transfer function from a perl function
98	# because that way perl saves all important things on
99	# the stack. Actually, I'd do it from within XS, but
100	# I couldn't get it to work.
101	sub transfer {
102	_transfer($_[0], $_[1]);
103	}	326	}
104		327
105	=item $error, $error_msg, $error_coro	328	=item $coroutine->on_destroy (\&cb)
106		329
107	This coroutine will be called on fatal errors. C<$error_msg> and	330	Registers a callback that is called when this coroutine gets destroyed,
108	C<$error_coro> return the error message and the error-causing coroutine	331	but before it is joined. The callback gets passed the terminate arguments,
109	(NOT an object) respectively. This API might change.	332	if any.
110		333
111	=cut	334	=cut
112		335
113	$error_msg =	336	sub on_destroy {
114	$error_coro = undef;	337	my ($self, $cb) = @_;
115		338
116	$error = _newprocess {	339	push @{ $self->{destroy_cb} }, $cb;
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	340	}
118	exit 50;	341
		342	=item $oldprio = $coroutine->prio ($newprio)
		343
		344	Sets (or gets, if the argument is missing) the priority of the
		345	coroutine. Higher priority coroutines get run before lower priority
		346	coroutines. Priorities are small signed integers (currently -4 .. +3),
		347	that you can refer to using PRIO_xxx constants (use the import tag :prio
		348	to get then):
		349
		350	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		351	3 > 1 > 0 > -1 > -3 > -4
		352
		353	# set priority to HIGH
		354	current->prio(PRIO_HIGH);
		355
		356	The idle coroutine ($Coro::idle) always has a lower priority than any
		357	existing coroutine.
		358
		359	Changing the priority of the current coroutine will take effect immediately,
		360	but changing the priority of coroutines in the ready queue (but not
		361	running) will only take effect after the next schedule (of that
		362	coroutine). This is a bug that will be fixed in some future version.
		363
		364	=item $newprio = $coroutine->nice ($change)
		365
		366	Similar to C<prio>, but subtract the given value from the priority (i.e.
		367	higher values mean lower priority, just as in unix).
		368
		369	=item $olddesc = $coroutine->desc ($newdesc)
		370
		371	Sets (or gets in case the argument is missing) the description for this
		372	coroutine. This is just a free-form string you can associate with a coroutine.
		373
		374	=cut
		375
		376	sub desc {
		377	my $old = $_[0]{desc};
		378	$_[0]{desc} = $_[1] if @_ > 1;
		379	$old;
		380	}
		381
		382	=back
		383
		384	=head2 GLOBAL FUNCTIONS
		385
		386	=over 4
		387
		388	=item Coro::nready
		389
		390	Returns the number of coroutines that are currently in the ready state,
		391	i.e. that can be swicthed to. The value C<0> means that the only runnable
		392	coroutine is the currently running one, so C<cede> would have no effect,
		393	and C<schedule> would cause a deadlock unless there is an idle handler
		394	that wakes up some coroutines.
		395
		396	=item unblock_sub { ... }
		397
		398	This utility function takes a BLOCK or code reference and "unblocks" it,
		399	returning the new coderef. This means that the new coderef will return
		400	immediately without blocking, returning nothing, while the original code
		401	ref will be called (with parameters) from within its own coroutine.
		402
		403	The reason this fucntion exists is that many event libraries (such as the
		404	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		405	of thread-safety). This means you must not block within event callbacks,
		406	otherwise you might suffer from crashes or worse.
		407
		408	This function allows your callbacks to block by executing them in another
		409	coroutine where it is safe to block. One example where blocking is handy
		410	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		411	disk.
		412
		413	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		414	creating event callbacks that want to block.
		415
		416	=cut
		417
		418	our @unblock_pool;
		419	our @unblock_queue;
		420	our $UNBLOCK_POOL_SIZE = 2;
		421
		422	sub unblock_handler_ {
		423	while () {
		424	my ($cb, @arg) = @{ delete $Coro::current->{arg} };
		425	$cb->(@arg);
		426
		427	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
		428	push @unblock_pool, $Coro::current;
		429	schedule;
		430	}
		431	}
		432
		433	our $unblock_scheduler = async {
		434	while () {
		435	while (my $cb = pop @unblock_queue) {
		436	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);
		437	$handler->{arg} = $cb;
		438	$handler->ready;
		439	cede;
		440	}
		441
		442	schedule;
		443	}
119	};	444	};
120		445
		446	sub unblock_sub(&) {
		447	my $cb = shift;
		448
		449	sub {
		450	push @unblock_queue, [$cb, @_];
		451	$unblock_scheduler->ready;
		452	}
		453	}
		454
		455	=back
		456
		457	=cut
		458
121	1;	459	1;
122		460
123	=back	461	=head1 BUGS/LIMITATIONS
124		462
125	=head1 BUGS	463	- you must make very sure that no coro is still active on global
		464	destruction. very bad things might happen otherwise (usually segfaults).
126		465
127	This module has not yet been extensively tested.	466	- this module is not thread-safe. You should only ever use this module
		467	from the same thread (this requirement might be losened in the future
		468	to allow per-thread schedulers, but Coro::State does not yet allow
		469	this).
128		470
129	=head1 SEE ALSO	471	=head1 SEE ALSO
130		472
131	L<Coro::Process>, L<Coro::Signal>.	473	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		474
		475	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		476
		477	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		478
		479	Embedding: L<Coro:MakeMaker>
132		480
133	=head1 AUTHOR	481	=head1 AUTHOR
134		482
135	Marc Lehmann <pcg@goof.com>	483	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	484	http://home.schmorp.de/
137		485
138	=cut	486	=cut
139		487

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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 1.102 by root, Fri Dec 29 11:37:49 2006 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 1.102 by root, Fri Dec 29 11:37:49 2006 UTC