[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 1.98 by root, Mon Dec 4 21:56:00 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 $VERSION = '3.1';
		56
		57	our @EXPORT = qw(async cede schedule terminate current unblock_sub);
		58	our %EXPORT_TAGS = (
		59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		60	);
		61	our @EXPORT_OK = (@{$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;
		158	$coro->{status} \|\|= [];
		159	$_->ready for @{delete $coro->{join} \|\| []};
49		160
50	Create a new coroutine and return it. The first C<transfer> call to this	161	# the next line destroys the coro state, but keeps the
51	coroutine will start execution at the given coderef. If, the subroutine	162	# coroutine itself intact (we basically make it a zombie
52	returns it will be executed again.	163	# coroutine that always runs the manager thread, so it's possible
		164	# to transfer() to this coroutine).
		165	$coro->_clone_state_from ($manager);
		166	}
		167	&schedule;
		168	}
		169	};
53		170
54	If the coderef is omitted this function will create a new "empty"	171	# static methods. not really.
55	coroutine, i.e. a coroutine that cannot be transfered to but can be used
56	to save the current coroutine in.
57		172
		173	=back
		174
		175	=head2 STATIC METHODS
		176
		177	Static methods are actually functions that operate on the current coroutine only.
		178
		179	=over 4
		180
		181	=item async { ... } [@args...]
		182
		183	Create a new asynchronous coroutine and return it's coroutine object
		184	(usually unused). When the sub returns the new coroutine is automatically
		185	terminated.
		186
		187	Calling C<exit> in a coroutine will not work correctly, so do not do that.
		188
		189	When the coroutine dies, the program will exit, just as in the main
		190	program.
		191
		192	# create a new coroutine that just prints its arguments
		193	async {
		194	print "@_\n";
		195	} 1,2,3,4;
		196
58	=cut	197	=cut
		198
		199	sub async(&@) {
		200	my $pid = new Coro @_;
		201	$pid->ready;
		202	$pid
		203	}
		204
		205	=item schedule
		206
		207	Calls the scheduler. Please note that the current coroutine will not be put
		208	into the ready queue, so calling this function usually means you will
		209	never be called again unless something else (e.g. an event handler) calls
		210	ready.
		211
		212	The canonical way to wait on external events is this:
		213
		214	{
		215	# remember current coroutine
		216	my $current = $Coro::current;
		217
		218	# register a hypothetical event handler
		219	on_event_invoke sub {
		220	# wake up sleeping coroutine
		221	$current->ready;
		222	undef $current;
		223	};
		224
		225	# call schedule until event occured.
		226	# in case we are woken up for other reasons
		227	# (current still defined), loop.
		228	Coro::schedule while $current;
		229	}
		230
		231	=item cede
		232
		233	"Cede" to other coroutines. This function puts the current coroutine into the
		234	ready queue and calls C<schedule>, which has the effect of giving up the
		235	current "timeslice" to other coroutines of the same or higher priority.
		236
		237	=item terminate [arg...]
		238
		239	Terminates the current coroutine with the given status values (see L<cancel>).
		240
		241	=cut
		242
		243	sub terminate {
		244	$current->cancel (@_);
		245	}
		246
		247	=back
		248
		249	# dynamic methods
		250
		251	=head2 COROUTINE METHODS
		252
		253	These are the methods you can call on coroutine objects.
		254
		255	=over 4
		256
		257	=item new Coro \&sub [, @args...]
		258
		259	Create a new coroutine and return it. When the sub returns the coroutine
		260	automatically terminates as if C<terminate> with the returned values were
		261	called. To make the coroutine run you must first put it into the ready queue
		262	by calling the ready method.
		263
		264	Calling C<exit> in a coroutine will not work correctly, so do not do that.
		265
		266	=cut
		267
		268	sub _run_coro {
		269	terminate &{+shift};
		270	}
59		271
60	sub new {	272	sub new {
61	my $class = $_[0];	273	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		274
75	=item $prev->transfer($next)	275	$class->SUPER::new (\&_run_coro, @_)
		276	}
76		277
77	Save the state of the current subroutine in C<$prev> and switch to the	278	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		279
80	The "state" of a subroutine only ever includes scope, i.e. lexical	280	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	281	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	282	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		283
88	The easiest way to do this is to create your own scheduling primitive like this:	284	=item $is_ready = $coroutine->is_ready
89		285
90	sub schedule {	286	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	287
92	$old->transfer($new);	288	=item $coroutine->cancel (arg...)
		289
		290	Terminates the given coroutine and makes it return the given arguments as
		291	status (default: the empty list).
		292
		293	=cut
		294
		295	sub cancel {
		296	my $self = shift;
		297	$self->{status} = [@_];
		298	push @destroy, $self;
		299	$manager->ready;
		300	&schedule if $current == $self;
		301	}
		302
		303	=item $coroutine->join
		304
		305	Wait until the coroutine terminates and return any values given to the
		306	C<terminate> or C<cancel> functions. C<join> can be called multiple times
		307	from multiple coroutine.
		308
		309	=cut
		310
		311	sub join {
		312	my $self = shift;
		313	unless ($self->{status}) {
		314	push @{$self->{join}}, $current;
		315	&schedule;
93	}	316	}
94		317	wantarray ? @{$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	}	318	}
104		319
105	=item $error, $error_msg, $error_coro	320	=item $oldprio = $coroutine->prio ($newprio)
106		321
107	This coroutine will be called on fatal errors. C<$error_msg> and	322	Sets (or gets, if the argument is missing) the priority of the
108	C<$error_coro> return the error message and the error-causing coroutine	323	coroutine. Higher priority coroutines get run before lower priority
109	(NOT an object) respectively. This API might change.	324	coroutines. Priorities are small signed integers (currently -4 .. +3),
		325	that you can refer to using PRIO_xxx constants (use the import tag :prio
		326	to get then):
110		327
111	=cut	328	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		329	3 > 1 > 0 > -1 > -3 > -4
112		330
113	$error_msg =	331	# set priority to HIGH
114	$error_coro = undef;	332	current->prio(PRIO_HIGH);
115		333
116	$error = _newprocess {	334	The idle coroutine ($Coro::idle) always has a lower priority than any
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	335	existing coroutine.
118	exit 50;	336
		337	Changing the priority of the current coroutine will take effect immediately,
		338	but changing the priority of coroutines in the ready queue (but not
		339	running) will only take effect after the next schedule (of that
		340	coroutine). This is a bug that will be fixed in some future version.
		341
		342	=item $newprio = $coroutine->nice ($change)
		343
		344	Similar to C<prio>, but subtract the given value from the priority (i.e.
		345	higher values mean lower priority, just as in unix).
		346
		347	=item $olddesc = $coroutine->desc ($newdesc)
		348
		349	Sets (or gets in case the argument is missing) the description for this
		350	coroutine. This is just a free-form string you can associate with a coroutine.
		351
		352	=cut
		353
		354	sub desc {
		355	my $old = $_[0]{desc};
		356	$_[0]{desc} = $_[1] if @_ > 1;
		357	$old;
		358	}
		359
		360	=back
		361
		362	=head2 GLOBAL FUNCTIONS
		363
		364	=over 4
		365
		366	=item Coro::nready
		367
		368	Returns the number of coroutines that are currently in the ready state,
		369	i.e. that can be swicthed to. The value C<0> means that the only runnable
		370	coroutine is the currently running one, so C<cede> would have no effect,
		371	and C<schedule> would cause a deadlock unless there is an idle handler
		372	that wakes up some coroutines.
		373
		374	=item unblock_sub { ... }
		375
		376	This utility function takes a BLOCK or code reference and "unblocks" it,
		377	returning the new coderef. This means that the new coderef will return
		378	immediately without blocking, returning nothing, while the original code
		379	ref will be called (with parameters) from within its own coroutine.
		380
		381	The reason this fucntion exists is that many event libraries (such as the
		382	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		383	of thread-safety). This means you must not block within event callbacks,
		384	otherwise you might suffer from crashes or worse.
		385
		386	This function allows your callbacks to block by executing them in another
		387	coroutine where it is safe to block. One example where blocking is handy
		388	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		389	disk.
		390
		391	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		392	creating event callbacks that want to block.
		393
		394	=cut
		395
		396	our @unblock_pool;
		397	our @unblock_queue;
		398	our $UNBLOCK_POOL_SIZE = 2;
		399
		400	sub unblock_handler_ {
		401	while () {
		402	my ($cb, @arg) = @{ delete $Coro::current->{arg} };
		403	$cb->(@arg);
		404
		405	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
		406	push @unblock_pool, $Coro::current;
		407	schedule;
		408	}
		409	}
		410
		411	our $unblock_scheduler = async {
		412	while () {
		413	while (my $cb = pop @unblock_queue) {
		414	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);
		415	$handler->{arg} = $cb;
		416	$handler->ready;
		417	cede;
		418	}
		419
		420	schedule;
		421	}
119	};	422	};
120		423
		424	sub unblock_sub(&) {
		425	my $cb = shift;
		426
		427	sub {
		428	push @unblock_queue, [$cb, @_];
		429	$unblock_scheduler->ready;
		430	}
		431	}
		432
		433	=back
		434
		435	=cut
		436
121	1;	437	1;
122		438
123	=back	439	=head1 BUGS/LIMITATIONS
124		440
125	=head1 BUGS	441	- you must make very sure that no coro is still active on global
		442	destruction. very bad things might happen otherwise (usually segfaults).
126		443
127	This module has not yet been extensively tested.	444	- this module is not thread-safe. You should only ever use this module
		445	from the same thread (this requirement might be losened in the future
		446	to allow per-thread schedulers, but Coro::State does not yet allow
		447	this).
128		448
129	=head1 SEE ALSO	449	=head1 SEE ALSO
130		450
131	L<Coro::Process>, L<Coro::Signal>.	451	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		452
		453	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		454
		455	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		456
		457	Embedding: L<Coro:MakeMaker>
132		458
133	=head1 AUTHOR	459	=head1 AUTHOR
134		460
135	Marc Lehmann <pcg@goof.com>	461	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	462	http://home.schmorp.de/
137		463
138	=cut	464	=cut
139		465

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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 1.98 by root, Mon Dec 4 21:56:00 2006 UTC

Diff Legend

Comparing Coro/Coro.pm (file contents):
Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs.
Revision 1.98 by root, Mon Dec 4 21:56:00 2006 UTC