[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 1.92 by root, Fri Dec 1 03:47:55 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 to
27	allow you to run more than one "thread of execution" in parallel. Unlike	24	threads but don't run in parallel.
28	threads this, only voluntary switching is used so locking problems are
29	greatly reduced.
30		25
31	Although this is the "main" module of the Coro family it provides only	26	In this module, coroutines are defined as "callchain + lexical variables
32	low-level functionality. See L<Coro::Process> and related modules for a	27	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
33	more useful process abstraction including scheduling.	28	callchain, it's own set of lexicals and it's own set of perl's most
		29	important global variables.
		30
		31	=cut
		32
		33	package Coro;
		34
		35	use strict;
		36	no warnings "uninitialized";
		37
		38	use Coro::State;
		39
		40	use base qw(Coro::State Exporter);
		41
		42	our $idle; # idle handler
		43	our $main; # main coroutine
		44	our $current; # current coroutine
		45
		46	our $VERSION = '3.0';
		47
		48	our @EXPORT = qw(async cede schedule terminate current unblock_sub);
		49	our %EXPORT_TAGS = (
		50	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		51	);
		52	our @EXPORT_OK = @{$EXPORT_TAGS{prio}};
		53
		54	{
		55	my @async;
		56	my $init;
		57
		58	# this way of handling attributes simply is NOT scalable ;()
		59	sub import {
		60	no strict 'refs';
		61
		62	Coro->export_to_level(1, @_);
		63
		64	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
		65	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
		66	my ($package, $ref) = (shift, shift);
		67	my @attrs;
		68	for (@_) {
		69	if ($_ eq "Coro") {
		70	push @async, $ref;
		71	unless ($init++) {
		72	eval q{
		73	sub INIT {
		74	&async(pop @async) while @async;
		75	}
		76	};
		77	}
		78	} else {
		79	push @attrs, $_;
		80	}
		81	}
		82	return $old ? $old->($package, $ref, @attrs) : @attrs;
		83	};
		84	}
		85
		86	}
34		87
35	=over 4	88	=over 4
36		89
37	=cut	90	=item $main
38		91
39	package Coro;	92	This coroutine represents the main program.
40		93
41	BEGIN {
42	$VERSION = 0.03;
43
44	require XSLoader;
45	XSLoader::load Coro, $VERSION;
46	}
47
48	=item $coro = new [$coderef [, @args]]
49
50	Create a new coroutine and return it. The first C<transfer> call to this
51	coroutine will start execution at the given coderef. If, the subroutine
52	returns it will be executed again.
53
54	If the coderef is omitted this function will create a new "empty"
55	coroutine, i.e. a coroutine that cannot be transfered to but can be used
56	to save the current coroutine in.
57
58	=cut	94	=cut
		95
		96	$main = new Coro;
		97
		98	=item $current (or as function: current)
		99
		100	The current coroutine (the last coroutine switched to). The initial value
		101	is C<$main> (of course).
		102
		103	This variable is B<strictly> I<read-only>. It is provided for performance
		104	reasons. If performance is not essentiel you are encouraged to use the
		105	C<Coro::current> function instead.
		106
		107	=cut
		108
		109	# maybe some other module used Coro::Specific before...
		110	if ($current) {
		111	$main->{specific} = $current->{specific};
		112	}
		113
		114	$current = $main;
		115
		116	sub current() { $current }
		117
		118	=item $idle
		119
		120	A callback that is called whenever the scheduler finds no ready coroutines
		121	to run. The default implementation prints "FATAL: deadlock detected" and
		122	exits, because the program has no other way to continue.
		123
		124	This hook is overwritten by modules such as C<Coro::Timer> and
		125	C<Coro::Event> to wait on an external event that hopefully wake up a
		126	coroutine so the scheduler can run it.
		127
		128	Please note that if your callback recursively invokes perl (e.g. for event
		129	handlers), then it must be prepared to be called recursively.
		130
		131	=cut
		132
		133	$idle = sub {
		134	print STDERR "FATAL: deadlock detected\n";
		135	exit (51);
		136	};
		137
		138	# this coroutine is necessary because a coroutine
		139	# cannot destroy itself.
		140	my @destroy;
		141	my $manager; $manager = new Coro sub {
		142	while () {
		143	# by overwriting the state object with the manager we destroy it
		144	# while still being able to schedule this coroutine (in case it has
		145	# been readied multiple times. this is harmless since the manager
		146	# can be called as many times as neccessary and will always
		147	# remove itself from the runqueue
		148	while (@destroy) {
		149	my $coro = pop @destroy;
		150	$coro->{status} \|\|= [];
		151	$_->ready for @{delete $coro->{join} \|\| []};
		152
		153	# the next line destroys the coro state, but keeps the
		154	# coroutine itself intact (we basically make it a zombie
		155	# coroutine that always runs the manager thread, so it's possible
		156	# to transfer() to this coroutine).
		157	$coro->_clone_state_from ($manager);
		158	}
		159	&schedule;
		160	}
		161	};
		162
		163	# static methods. not really.
		164
		165	=back
		166
		167	=head2 STATIC METHODS
		168
		169	Static methods are actually functions that operate on the current coroutine only.
		170
		171	=over 4
		172
		173	=item async { ... } [@args...]
		174
		175	Create a new asynchronous coroutine and return it's coroutine object
		176	(usually unused). When the sub returns the new coroutine is automatically
		177	terminated.
		178
		179	Calling C<exit> in a coroutine will not work correctly, so do not do that.
		180
		181	When the coroutine dies, the program will exit, just as in the main
		182	program.
		183
		184	# create a new coroutine that just prints its arguments
		185	async {
		186	print "@_\n";
		187	} 1,2,3,4;
		188
		189	=cut
		190
		191	sub async(&@) {
		192	my $pid = new Coro @_;
		193	$pid->ready;
		194	$pid
		195	}
		196
		197	=item schedule
		198
		199	Calls the scheduler. Please note that the current coroutine will not be put
		200	into the ready queue, so calling this function usually means you will
		201	never be called again unless something else (e.g. an event handler) calls
		202	ready.
		203
		204	The canonical way to wait on external events is this:
		205
		206	{
		207	# remember current coroutine
		208	my $current = $Coro::current;
		209
		210	# register a hypothetical event handler
		211	on_event_invoke sub {
		212	# wake up sleeping coroutine
		213	$current->ready;
		214	undef $current;
		215	};
		216
		217	# call schedule until event occured.
		218	# in case we are woken up for other reasons
		219	# (current still defined), loop.
		220	Coro::schedule while $current;
		221	}
		222
		223	=item cede
		224
		225	"Cede" to other coroutines. This function puts the current coroutine into the
		226	ready queue and calls C<schedule>, which has the effect of giving up the
		227	current "timeslice" to other coroutines of the same or higher priority.
		228
		229	=item terminate [arg...]
		230
		231	Terminates the current coroutine with the given status values (see L<cancel>).
		232
		233	=cut
		234
		235	sub terminate {
		236	$current->cancel (@_);
		237	}
		238
		239	=back
		240
		241	# dynamic methods
		242
		243	=head2 COROUTINE METHODS
		244
		245	These are the methods you can call on coroutine objects.
		246
		247	=over 4
		248
		249	=item new Coro \&sub [, @args...]
		250
		251	Create a new coroutine and return it. When the sub returns the coroutine
		252	automatically terminates as if C<terminate> with the returned values were
		253	called. To make the coroutine run you must first put it into the ready queue
		254	by calling the ready method.
		255
		256	Calling C<exit> in a coroutine will not work correctly, so do not do that.
		257
		258	=cut
		259
		260	sub _new_coro {
		261	terminate &{+shift};
		262	}
59		263
60	sub new {	264	sub new {
61	my $class = $_[0];	265	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		266
75	=item $prev->transfer($next)	267	$class->SUPER::new (\&_new_coro, @_)
		268	}
76		269
77	Save the state of the current subroutine in C<$prev> and switch to the	270	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		271
80	The "state" of a subroutine only ever includes scope, i.e. lexical	272	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	273	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	274	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		275
88	The easiest way to do this is to create your own scheduling primitive like this:	276	=item $is_ready = $coroutine->is_ready
89		277
90	sub schedule {	278	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	279
92	$old->transfer($new);	280	=item $coroutine->cancel (arg...)
		281
		282	Terminates the given coroutine and makes it return the given arguments as
		283	status (default: the empty list).
		284
		285	=cut
		286
		287	sub cancel {
		288	my $self = shift;
		289	$self->{status} = [@_];
		290	push @destroy, $self;
		291	$manager->ready;
		292	&schedule if $current == $self;
		293	}
		294
		295	=item $coroutine->join
		296
		297	Wait until the coroutine terminates and return any values given to the
		298	C<terminate> or C<cancel> functions. C<join> can be called multiple times
		299	from multiple coroutine.
		300
		301	=cut
		302
		303	sub join {
		304	my $self = shift;
		305	unless ($self->{status}) {
		306	push @{$self->{join}}, $current;
		307	&schedule;
93	}	308	}
94		309	wantarray ? @{$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	}	310	}
104		311
105	=item $error, $error_msg, $error_coro	312	=item $oldprio = $coroutine->prio ($newprio)
106		313
107	This coroutine will be called on fatal errors. C<$error_msg> and	314	Sets (or gets, if the argument is missing) the priority of the
108	C<$error_coro> return the error message and the error-causing coroutine	315	coroutine. Higher priority coroutines get run before lower priority
109	(NOT an object) respectively. This API might change.	316	coroutines. Priorities are small signed integers (currently -4 .. +3),
		317	that you can refer to using PRIO_xxx constants (use the import tag :prio
		318	to get then):
110		319
111	=cut	320	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		321	3 > 1 > 0 > -1 > -3 > -4
112		322
113	$error_msg =	323	# set priority to HIGH
114	$error_coro = undef;	324	current->prio(PRIO_HIGH);
115		325
116	$error = _newprocess {	326	The idle coroutine ($Coro::idle) always has a lower priority than any
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	327	existing coroutine.
118	exit 50;	328
		329	Changing the priority of the current coroutine will take effect immediately,
		330	but changing the priority of coroutines in the ready queue (but not
		331	running) will only take effect after the next schedule (of that
		332	coroutine). This is a bug that will be fixed in some future version.
		333
		334	=item $newprio = $coroutine->nice ($change)
		335
		336	Similar to C<prio>, but subtract the given value from the priority (i.e.
		337	higher values mean lower priority, just as in unix).
		338
		339	=item $olddesc = $coroutine->desc ($newdesc)
		340
		341	Sets (or gets in case the argument is missing) the description for this
		342	coroutine. This is just a free-form string you can associate with a coroutine.
		343
		344	=cut
		345
		346	sub desc {
		347	my $old = $_[0]{desc};
		348	$_[0]{desc} = $_[1] if @_ > 1;
		349	$old;
		350	}
		351
		352	=back
		353
		354	=head2 UTILITY FUNCTIONS
		355
		356	=over 4
		357
		358	=item unblock_sub { ... }
		359
		360	This utility function takes a BLOCK or code reference and "unblocks" it,
		361	returning the new coderef. This means that the new coderef will return
		362	immediately without blocking, returning nothing, while the original code
		363	ref will be called (with parameters) from within its own coroutine.
		364
		365	The reason this fucntion exists is that many event libraries (such as the
		366	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		367	of thread-safety). This means you must not block within event callbacks,
		368	otherwise you might suffer from crashes or worse.
		369
		370	This function allows your callbacks to block by executing them in another
		371	coroutine where it is safe to block. One example where blocking is handy
		372	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		373	disk.
		374
		375	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		376	creating event callbacks that want to block.
		377
		378	=cut
		379
		380	our @unblock_pool;
		381	our @unblock_queue;
		382	our $UNBLOCK_POOL_SIZE = 2;
		383
		384	sub unblock_handler_ {
		385	while () {
		386	my ($cb, @arg) = @{ delete $Coro::current->{arg} };
		387	$cb->(@arg);
		388
		389	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
		390	push @unblock_pool, $Coro::current;
		391	schedule;
		392	}
		393	}
		394
		395	our $unblock_scheduler = async {
		396	while () {
		397	while (my $cb = pop @unblock_queue) {
		398	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);
		399	$handler->{arg} = $cb;
		400	$handler->ready;
		401	cede;
		402	}
		403
		404	schedule;
		405	}
119	};	406	};
120		407
		408	sub unblock_sub(&) {
		409	my $cb = shift;
		410
		411	sub {
		412	push @unblock_queue, [$cb, @_];
		413	$unblock_scheduler->ready;
		414	}
		415	}
		416
		417	=back
		418
		419	=cut
		420
121	1;	421	1;
122		422
123	=back	423	=head1 BUGS/LIMITATIONS
124		424
125	=head1 BUGS	425	- you must make very sure that no coro is still active on global
		426	destruction. very bad things might happen otherwise (usually segfaults).
126		427
127	This module has not yet been extensively tested.	428	- this module is not thread-safe. You should only ever use this module
		429	from the same thread (this requirement might be losened in the future
		430	to allow per-thread schedulers, but Coro::State does not yet allow
		431	this).
128		432
129	=head1 SEE ALSO	433	=head1 SEE ALSO
130		434
131	L<Coro::Process>, L<Coro::Signal>.	435	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		436
		437	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		438
		439	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		440
		441	Embedding: L<Coro:MakeMaker>
132		442
133	=head1 AUTHOR	443	=head1 AUTHOR
134		444
135	Marc Lehmann <pcg@goof.com>	445	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	446	http://home.schmorp.de/
137		447
138	=cut	448	=cut
139		449

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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 1.92 by root, Fri Dec 1 03:47:55 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 1.92 by root, Fri Dec 1 03:47:55 2006 UTC