[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 1.95 by root, Sun Dec 3 22:50:06 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 $VERSION = '3.01';
		47
		48	our @EXPORT = qw(async cede schedule terminate current unblock_sub);
		49	our %EXPORT_TAGS = (
		50	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		51	);
		52	our @EXPORT_OK = @{$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	$main->{specific} = $current->{specific}
		111	if $current;
		112
		113	_set_current $main;
		114
		115	sub current() { $current }
		116
		117	=item $idle
		118
		119	A callback that is called whenever the scheduler finds no ready coroutines
		120	to run. The default implementation prints "FATAL: deadlock detected" and
		121	exits, because the program has no other way to continue.
		122
		123	This hook is overwritten by modules such as C<Coro::Timer> and
		124	C<Coro::Event> to wait on an external event that hopefully wake up a
		125	coroutine so the scheduler can run it.
		126
		127	Please note that if your callback recursively invokes perl (e.g. for event
		128	handlers), then it must be prepared to be called recursively.
		129
		130	=cut
		131
		132	$idle = sub {
		133	print STDERR "FATAL: deadlock detected\n";
		134	exit (51);
		135	};
		136
		137	# this coroutine is necessary because a coroutine
		138	# cannot destroy itself.
		139	my @destroy;
		140	my $manager; $manager = new Coro sub {
		141	while () {
		142	# by overwriting the state object with the manager we destroy it
		143	# while still being able to schedule this coroutine (in case it has
		144	# been readied multiple times. this is harmless since the manager
		145	# can be called as many times as neccessary and will always
		146	# remove itself from the runqueue
		147	while (@destroy) {
		148	my $coro = pop @destroy;
		149	$coro->{status} \|\|= [];
		150	$_->ready for @{delete $coro->{join} \|\| []};
		151
		152	# the next line destroys the coro state, but keeps the
		153	# coroutine itself intact (we basically make it a zombie
		154	# coroutine that always runs the manager thread, so it's possible
		155	# to transfer() to this coroutine).
		156	$coro->_clone_state_from ($manager);
		157	}
		158	&schedule;
		159	}
		160	};
		161
		162	# static methods. not really.
		163
		164	=back
		165
		166	=head2 STATIC METHODS
		167
		168	Static methods are actually functions that operate on the current coroutine only.
		169
		170	=over 4
		171
		172	=item async { ... } [@args...]
		173
		174	Create a new asynchronous coroutine and return it's coroutine object
		175	(usually unused). When the sub returns the new coroutine is automatically
		176	terminated.
		177
		178	Calling C<exit> in a coroutine will not work correctly, so do not do that.
		179
		180	When the coroutine dies, the program will exit, just as in the main
		181	program.
		182
		183	# create a new coroutine that just prints its arguments
		184	async {
		185	print "@_\n";
		186	} 1,2,3,4;
		187
		188	=cut
		189
		190	sub async(&@) {
		191	my $pid = new Coro @_;
		192	$pid->ready;
		193	$pid
		194	}
		195
		196	=item schedule
		197
		198	Calls the scheduler. Please note that the current coroutine will not be put
		199	into the ready queue, so calling this function usually means you will
		200	never be called again unless something else (e.g. an event handler) calls
		201	ready.
		202
		203	The canonical way to wait on external events is this:
		204
		205	{
		206	# remember current coroutine
		207	my $current = $Coro::current;
		208
		209	# register a hypothetical event handler
		210	on_event_invoke sub {
		211	# wake up sleeping coroutine
		212	$current->ready;
		213	undef $current;
		214	};
		215
		216	# call schedule until event occured.
		217	# in case we are woken up for other reasons
		218	# (current still defined), loop.
		219	Coro::schedule while $current;
		220	}
		221
		222	=item cede
		223
		224	"Cede" to other coroutines. This function puts the current coroutine into the
		225	ready queue and calls C<schedule>, which has the effect of giving up the
		226	current "timeslice" to other coroutines of the same or higher priority.
		227
		228	=item terminate [arg...]
		229
		230	Terminates the current coroutine with the given status values (see L<cancel>).
		231
		232	=cut
		233
		234	sub terminate {
		235	$current->cancel (@_);
		236	}
		237
		238	=back
		239
		240	# dynamic methods
		241
		242	=head2 COROUTINE METHODS
		243
		244	These are the methods you can call on coroutine objects.
		245
		246	=over 4
		247
		248	=item new Coro \&sub [, @args...]
		249
		250	Create a new coroutine and return it. When the sub returns the coroutine
		251	automatically terminates as if C<terminate> with the returned values were
		252	called. To make the coroutine run you must first put it into the ready queue
		253	by calling the ready method.
		254
		255	Calling C<exit> in a coroutine will not work correctly, so do not do that.
		256
		257	=cut
		258
		259	sub _run_coro {
		260	terminate &{+shift};
		261	}
59		262
60	sub new {	263	sub new {
61	my $class = $_[0];	264	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		265
75	=item $prev->transfer($next)	266	$class->SUPER::new (\&_run_coro, @_)
		267	}
76		268
77	Save the state of the current subroutine in C<$prev> and switch to the	269	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		270
80	The "state" of a subroutine only ever includes scope, i.e. lexical	271	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	272	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	273	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		274
88	The easiest way to do this is to create your own scheduling primitive like this:	275	=item $is_ready = $coroutine->is_ready
89		276
90	sub schedule {	277	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	278
92	$old->transfer($new);	279	=item $coroutine->cancel (arg...)
		280
		281	Terminates the given coroutine and makes it return the given arguments as
		282	status (default: the empty list).
		283
		284	=cut
		285
		286	sub cancel {
		287	my $self = shift;
		288	$self->{status} = [@_];
		289	push @destroy, $self;
		290	$manager->ready;
		291	&schedule if $current == $self;
		292	}
		293
		294	=item $coroutine->join
		295
		296	Wait until the coroutine terminates and return any values given to the
		297	C<terminate> or C<cancel> functions. C<join> can be called multiple times
		298	from multiple coroutine.
		299
		300	=cut
		301
		302	sub join {
		303	my $self = shift;
		304	unless ($self->{status}) {
		305	push @{$self->{join}}, $current;
		306	&schedule;
93	}	307	}
94		308	wantarray ? @{$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	}	309	}
104		310
105	=item $error, $error_msg, $error_coro	311	=item $oldprio = $coroutine->prio ($newprio)
106		312
107	This coroutine will be called on fatal errors. C<$error_msg> and	313	Sets (or gets, if the argument is missing) the priority of the
108	C<$error_coro> return the error message and the error-causing coroutine	314	coroutine. Higher priority coroutines get run before lower priority
109	(NOT an object) respectively. This API might change.	315	coroutines. Priorities are small signed integers (currently -4 .. +3),
		316	that you can refer to using PRIO_xxx constants (use the import tag :prio
		317	to get then):
110		318
111	=cut	319	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		320	3 > 1 > 0 > -1 > -3 > -4
112		321
113	$error_msg =	322	# set priority to HIGH
114	$error_coro = undef;	323	current->prio(PRIO_HIGH);
115		324
116	$error = _newprocess {	325	The idle coroutine ($Coro::idle) always has a lower priority than any
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	326	existing coroutine.
118	exit 50;	327
		328	Changing the priority of the current coroutine will take effect immediately,
		329	but changing the priority of coroutines in the ready queue (but not
		330	running) will only take effect after the next schedule (of that
		331	coroutine). This is a bug that will be fixed in some future version.
		332
		333	=item $newprio = $coroutine->nice ($change)
		334
		335	Similar to C<prio>, but subtract the given value from the priority (i.e.
		336	higher values mean lower priority, just as in unix).
		337
		338	=item $olddesc = $coroutine->desc ($newdesc)
		339
		340	Sets (or gets in case the argument is missing) the description for this
		341	coroutine. This is just a free-form string you can associate with a coroutine.
		342
		343	=cut
		344
		345	sub desc {
		346	my $old = $_[0]{desc};
		347	$_[0]{desc} = $_[1] if @_ > 1;
		348	$old;
		349	}
		350
		351	=back
		352
		353	=head2 UTILITY FUNCTIONS
		354
		355	=over 4
		356
		357	=item unblock_sub { ... }
		358
		359	This utility function takes a BLOCK or code reference and "unblocks" it,
		360	returning the new coderef. This means that the new coderef will return
		361	immediately without blocking, returning nothing, while the original code
		362	ref will be called (with parameters) from within its own coroutine.
		363
		364	The reason this fucntion exists is that many event libraries (such as the
		365	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		366	of thread-safety). This means you must not block within event callbacks,
		367	otherwise you might suffer from crashes or worse.
		368
		369	This function allows your callbacks to block by executing them in another
		370	coroutine where it is safe to block. One example where blocking is handy
		371	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		372	disk.
		373
		374	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		375	creating event callbacks that want to block.
		376
		377	=cut
		378
		379	our @unblock_pool;
		380	our @unblock_queue;
		381	our $UNBLOCK_POOL_SIZE = 2;
		382
		383	sub unblock_handler_ {
		384	while () {
		385	my ($cb, @arg) = @{ delete $Coro::current->{arg} };
		386	$cb->(@arg);
		387
		388	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
		389	push @unblock_pool, $Coro::current;
		390	schedule;
		391	}
		392	}
		393
		394	our $unblock_scheduler = async {
		395	while () {
		396	while (my $cb = pop @unblock_queue) {
		397	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);
		398	$handler->{arg} = $cb;
		399	$handler->ready;
		400	cede;
		401	}
		402
		403	schedule;
		404	}
119	};	405	};
120		406
		407	sub unblock_sub(&) {
		408	my $cb = shift;
		409
		410	sub {
		411	push @unblock_queue, [$cb, @_];
		412	$unblock_scheduler->ready;
		413	}
		414	}
		415
		416	=back
		417
		418	=cut
		419
121	1;	420	1;
122		421
123	=back	422	=head1 BUGS/LIMITATIONS
124		423
125	=head1 BUGS	424	- you must make very sure that no coro is still active on global
		425	destruction. very bad things might happen otherwise (usually segfaults).
126		426
127	This module has not yet been extensively tested.	427	- this module is not thread-safe. You should only ever use this module
		428	from the same thread (this requirement might be losened in the future
		429	to allow per-thread schedulers, but Coro::State does not yet allow
		430	this).
128		431
129	=head1 SEE ALSO	432	=head1 SEE ALSO
130		433
131	L<Coro::Process>, L<Coro::Signal>.	434	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		435
		436	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		437
		438	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		439
		440	Embedding: L<Coro:MakeMaker>
132		441
133	=head1 AUTHOR	442	=head1 AUTHOR
134		443
135	Marc Lehmann <pcg@goof.com>	444	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	445	http://home.schmorp.de/
137		446
138	=cut	447	=cut
139		448

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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 1.95 by root, Sun Dec 3 22:50:06 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 1.95 by root, Sun Dec 3 22:50:06 2006 UTC