[ViewVC] Diff of: cvs/Coro/Coro.pm

Comparing Coro/Coro.pm (file contents):
Revision 1.20 by root, Sat Jul 21 18:21:45 2001 UTC vs.
Revision 1.255 by root, Wed Jun 17 21:36:35 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - coroutine process abstraction	3	Coro - the only real threads in perl
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use Coro;	7	use Coro;
8		8
9	async {	9	async {
10	# some asynchronous thread of execution	10	# some asynchronous thread of execution
		11	print "2\n";
		12	cede; # yield back to main
		13	print "4\n";
11	};	14	};
12		15	print "1\n";
13	# alternatively create an async process like this:	16	cede; # yield to coro
14		17	print "3\n";
15	sub some_func : Coro {	18	cede; # and again
16	# some more async code	19
17	}	20	# use locking
18		21	use Coro::Semaphore;
19	yield;	22	my $lock = new Coro::Semaphore;
		23	my $locked;
		24
		25	$lock->down;
		26	$locked = 1;
		27	$lock->up;
20		28
21	=head1 DESCRIPTION	29	=head1 DESCRIPTION
22		30
23	This module collection manages coroutines. Coroutines are similar to	31	For a tutorial-style introduction, please read the L<Coro::Intro>
24	Threads but don't run in parallel.	32	manpage. This manpage mainly contains reference information.
25		33
26	This module is still experimental, see the BUGS section below.	34	This module collection manages continuations in general, most often in
		35	the form of cooperative threads (also called coros, or simply "coro"
		36	in the documentation). They are similar to kernel threads but don't (in
		37	general) run in parallel at the same time even on SMP machines. The
		38	specific flavor of thread offered by this module also guarantees you that
		39	it will not switch between threads unless necessary, at easily-identified
		40	points in your program, so locking and parallel access are rarely an
		41	issue, making thread programming much safer and easier than using other
		42	thread models.
27		43
		44	Unlike the so-called "Perl threads" (which are not actually real threads
		45	but only the windows process emulation ported to unix, and as such act
		46	as processes), Coro provides a full shared address space, which makes
		47	communication between threads very easy. And Coro's threads are fast,
		48	too: disabling the Windows process emulation code in your perl and using
		49	Coro can easily result in a two to four times speed increase for your
		50	programs. A parallel matrix multiplication benchmark runs over 300 times
		51	faster on a single core than perl's pseudo-threads on a quad core using
		52	all four cores.
		53
		54	Coro achieves that by supporting multiple running interpreters that share
		55	data, which is especially useful to code pseudo-parallel processes and
		56	for event-based programming, such as multiple HTTP-GET requests running
		57	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		58	into an event-based environment.
		59
28	In this module, coroutines are defined as "callchain + lexical variables	60	In this module, a thread is defined as "callchain + lexical variables +
29	+ @_ + $_ + $@ + $^W), that is, a coroutine has it's own callchain, it's	61	some package variables + C stack), that is, a thread has its own callchain,
30	own set of lexicals and it's own set of perl's most important global	62	its own set of lexicals and its own set of perls most important global
31	variables.	63	variables (see L<Coro::State> for more configuration and background info).
		64
		65	See also the C<SEE ALSO> section at the end of this document - the Coro
		66	module family is quite large.
32		67
33	=cut	68	=cut
34		69
35	package Coro;	70	package Coro;
36		71
		72	use strict qw(vars subs);
		73	no warnings "uninitialized";
		74
		75	use Guard ();
		76
37	use Coro::State;	77	use Coro::State;
38		78
39	use base Exporter;	79	use base qw(Coro::State Exporter);
40		80
		81	our $idle; # idle handler
		82	our $main; # main coro
		83	our $current; # current coro
		84
41	$VERSION = 0.10;	85	our $VERSION = 5.132;
42		86
43	@EXPORT = qw(async yield schedule terminate current);	87	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44	@EXPORT_OK = qw($current);	88	our %EXPORT_TAGS = (
		89	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		90	);
		91	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
45		92
46	{	93	=head1 GLOBAL VARIABLES
47	my @async;
48		94
49	# this way of handling attributes simply is NOT scalable ;()	95	=over 4
50	sub import {	96
51	Coro->export_to_level(1, @_);	97	=item $Coro::main
52	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};	98
53	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {	99	This variable stores the Coro object that represents the main
54	my ($package, $ref) = (shift, shift);	100	program. While you cna C<ready> it and do most other things you can do to
55	my @attrs;	101	coro, it is mainly useful to compare again C<$Coro::current>, to see
56	for (@_) {	102	whether you are running in the main program or not.
57	if ($_ eq "Coro") {	103
58	push @async, $ref;	104	=cut
59	} else {	105
60	push @attrs, $_;	106	# $main is now being initialised by Coro::State
61	}	107
62	}	108	=item $Coro::current
63	return $old ? $old->($package, $ref, @attrs) : @attrs;	109
64	};	110	The Coro object representing the current coro (the last
		111	coro that the Coro scheduler switched to). The initial value is
		112	C<$Coro::main> (of course).
		113
		114	This variable is B<strictly> I<read-only>. You can take copies of the
		115	value stored in it and use it as any other Coro object, but you must
		116	not otherwise modify the variable itself.
		117
		118	=cut
		119
		120	sub current() { $current } # [DEPRECATED]
		121
		122	=item $Coro::idle
		123
		124	This variable is mainly useful to integrate Coro into event loops. It is
		125	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		126	pretty low-level functionality.
		127
		128	This variable stores either a Coro object or a callback.
		129
		130	If it is a callback, the it is called whenever the scheduler finds no
		131	ready coros to run. The default implementation prints "FATAL:
		132	deadlock detected" and exits, because the program has no other way to
		133	continue.
		134
		135	If it is a coro object, then this object will be readied (without
		136	invoking any ready hooks, however) when the scheduler finds no other ready
		137	coros to run.
		138
		139	This hook is overwritten by modules such as C<Coro::EV> and
		140	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
		141	coro so the scheduler can run it.
		142
		143	Note that the callback I<must not>, under any circumstances, block
		144	the current coro. Normally, this is achieved by having an "idle
		145	coro" that calls the event loop and then blocks again, and then
		146	readying that coro in the idle handler, or by simply placing the idle
		147	coro in this variable.
		148
		149	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		150	technique.
		151
		152	Please note that if your callback recursively invokes perl (e.g. for event
		153	handlers), then it must be prepared to be called recursively itself.
		154
		155	=cut
		156
		157	$idle = sub {
		158	require Carp;
		159	Carp::croak ("FATAL: deadlock detected");
		160	};
		161
		162	# this coro is necessary because a coro
		163	# cannot destroy itself.
		164	our @destroy;
		165	our $manager;
		166
		167	$manager = new Coro sub {
		168	while () {
		169	Coro::State::cancel shift @destroy
		170	while @destroy;
		171
		172	&schedule;
65	}	173	}
66
67	sub INIT {
68	&async(pop @async) while @async;
69	}
70	}
71
72	=item $main
73
74	This coroutine represents the main program.
75
76	=cut
77
78	our $main = new Coro;
79
80	=item $current (or as function: current)
81
82	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
83
84	=cut
85
86	# maybe some other module used Coro::Specific before...
87	if ($current) {
88	$main->{specific} = $current->{specific};
89	}
90
91	our $current = $main;
92
93	sub current() { $current }
94
95	=item $idle
96
97	The coroutine to switch to when no other coroutine is running. The default
98	implementation prints "FATAL: deadlock detected" and exits.
99
100	=cut
101
102	# should be done using priorities :(
103	our $idle = new Coro sub {
104	print STDERR "FATAL: deadlock detected\n";
105	exit(51);
106	};	174	};
		175	$manager->{desc} = "[coro manager]";
		176	$manager->prio (PRIO_MAX);
107		177
108	# we really need priorities...	178	=back
109	my @ready; # the ready queue. hehe, rather broken ;)
110		179
111	# static methods. not really.	180	=head1 SIMPLE CORO CREATION
112
113	=head2 STATIC METHODS
114
115	Static methods are actually functions that operate on the current process only.
116		181
117	=over 4	182	=over 4
118		183
119	=item async { ... } [@args...]	184	=item async { ... } [@args...]
120		185
121	Create a new asynchronous process and return it's process object	186	Create a new coro and return its Coro object (usually
122	(usually unused). When the sub returns the new process is automatically	187	unused). The coro will be put into the ready queue, so
		188	it will start running automatically on the next scheduler run.
		189
		190	The first argument is a codeblock/closure that should be executed in the
		191	coro. When it returns argument returns the coro is automatically
123	terminated.	192	terminated.
124		193
		194	The remaining arguments are passed as arguments to the closure.
		195
		196	See the C<Coro::State::new> constructor for info about the coro
		197	environment in which coro are executed.
		198
		199	Calling C<exit> in a coro will do the same as calling exit outside
		200	the coro. Likewise, when the coro dies, the program will exit,
		201	just as it would in the main program.
		202
		203	If you do not want that, you can provide a default C<die> handler, or
		204	simply avoid dieing (by use of C<eval>).
		205
125	# create a new coroutine that just prints its arguments	206	Example: Create a new coro that just prints its arguments.
		207
126	async {	208	async {
127	print "@_\n";	209	print "@_\n";
128	} 1,2,3,4;	210	} 1,2,3,4;
129		211
130	The coderef you submit MUST NOT be a closure that refers to variables
131	in an outer scope. This does NOT work. Pass arguments into it instead.
132
133	=cut	212	=cut
134		213
135	sub async(&@) {	214	sub async(&@) {
136	my $pid = new Coro @_;	215	my $coro = new Coro @_;
137	$pid->ready;	216	$coro->ready;
138	$pid;	217	$coro
139	}	218	}
		219
		220	=item async_pool { ... } [@args...]
		221
		222	Similar to C<async>, but uses a coro pool, so you should not call
		223	terminate or join on it (although you are allowed to), and you get a
		224	coro that might have executed other code already (which can be good
		225	or bad :).
		226
		227	On the plus side, this function is about twice as fast as creating (and
		228	destroying) a completely new coro, so if you need a lot of generic
		229	coros in quick successsion, use C<async_pool>, not C<async>.
		230
		231	The code block is executed in an C<eval> context and a warning will be
		232	issued in case of an exception instead of terminating the program, as
		233	C<async> does. As the coro is being reused, stuff like C<on_destroy>
		234	will not work in the expected way, unless you call terminate or cancel,
		235	which somehow defeats the purpose of pooling (but is fine in the
		236	exceptional case).
		237
		238	The priority will be reset to C<0> after each run, tracing will be
		239	disabled, the description will be reset and the default output filehandle
		240	gets restored, so you can change all these. Otherwise the coro will
		241	be re-used "as-is": most notably if you change other per-coro global
		242	stuff such as C<$/> you I<must needs> revert that change, which is most
		243	simply done by using local as in: C<< local $/ >>.
		244
		245	The idle pool size is limited to C<8> idle coros (this can be
		246	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		247	coros as required.
		248
		249	If you are concerned about pooled coros growing a lot because a
		250	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		251	{ terminate }> once per second or so to slowly replenish the pool. In
		252	addition to that, when the stacks used by a handler grows larger than 32kb
		253	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		254
		255	=cut
		256
		257	our $POOL_SIZE = 8;
		258	our $POOL_RSS = 32 * 1024;
		259	our @async_pool;
		260
		261	sub pool_handler {
		262	while () {
		263	eval {
		264	&{&_pool_handler} while 1;
		265	};
		266
		267	warn $@ if $@;
		268	}
		269	}
		270
		271	=back
		272
		273	=head1 STATIC METHODS
		274
		275	Static methods are actually functions that implicitly operate on the
		276	current coro.
		277
		278	=over 4
140		279
141	=item schedule	280	=item schedule
142		281
143	Calls the scheduler. Please note that the current process will not be put	282	Calls the scheduler. The scheduler will find the next coro that is
		283	to be run from the ready queue and switches to it. The next coro
		284	to be run is simply the one with the highest priority that is longest
		285	in its ready queue. If there is no coro ready, it will clal the
		286	C<$Coro::idle> hook.
		287
		288	Please note that the current coro will I<not> be put into the ready
144	into the ready queue, so calling this function usually means you will	289	queue, so calling this function usually means you will never be called
145	never be called again.	290	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		291	thus waking you up.
146		292
147	=cut	293	This makes C<schedule> I<the> generic method to use to block the current
		294	coro and wait for events: first you remember the current coro in
		295	a variable, then arrange for some callback of yours to call C<< ->ready
		296	>> on that once some event happens, and last you call C<schedule> to put
		297	yourself to sleep. Note that a lot of things can wake your coro up,
		298	so you need to check whether the event indeed happened, e.g. by storing the
		299	status in a variable.
148		300
149	my $prev;	301	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
150		302
151	sub schedule {
152	# should be done using priorities :(
153	($prev, $current) = ($current, shift @ready \|\| $idle);
154	Coro::State::transfer($prev, $current);
155	}
156
157	=item yield	303	=item cede
158		304
159	Yield to other processes. This function puts the current process into the	305	"Cede" to other coros. This function puts the current coro into
160	ready queue and calls C<schedule>.	306	the ready queue and calls C<schedule>, which has the effect of giving
		307	up the current "timeslice" to other coros of the same or higher
		308	priority. Once your coro gets its turn again it will automatically be
		309	resumed.
161		310
162	=cut	311	This function is often called C<yield> in other languages.
163		312
164	sub yield {	313	=item Coro::cede_notself
165	$current->ready;
166	&schedule;
167	}
168		314
		315	Works like cede, but is not exported by default and will cede to I<any>
		316	coro, regardless of priority. This is useful sometimes to ensure
		317	progress is made.
		318
169	=item terminate	319	=item terminate [arg...]
170		320
171	Terminates the current process.	321	Terminates the current coro with the given status values (see L<cancel>).
172		322
173	Future versions of this function will allow result arguments.	323	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
174		324
175	=cut	325	These function install enter and leave winders in the current scope. The
		326	enter block will be executed when on_enter is called and whenever the
		327	current coro is re-entered by the scheduler, while the leave block is
		328	executed whenever the current coro is blocked by the scheduler, and
		329	also when the containing scope is exited (by whatever means, be it exit,
		330	die, last etc.).
176		331
177	sub terminate {	332	I<Neither invoking the scheduler, nor exceptions, are allowed within those
178	$current->{_results} = [@_];	333	BLOCKs>. That means: do not even think about calling C<die> without an
179	&schedule;	334	eval, and do not even think of entering the scheduler in any way.
		335
		336	Since both BLOCKs are tied to the current scope, they will automatically
		337	be removed when the current scope exits.
		338
		339	These functions implement the same concept as C<dynamic-wind> in scheme
		340	does, and are useful when you want to localise some resource to a specific
		341	coro.
		342
		343	They slow down thread switching considerably for coros that use them
		344	(about 40% for a BLOCK with a single assignment, so thread switching is
		345	still reasonably fast if the handlers are fast).
		346
		347	These functions are best understood by an example: The following function
		348	will change the current timezone to "Antarctica/South_Pole", which
		349	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		350	which remember/change the current timezone and restore the previous
		351	value, respectively, the timezone is only changed for the coro that
		352	installed those handlers.
		353
		354	use POSIX qw(tzset);
		355
		356	async {
		357	my $old_tz; # store outside TZ value here
		358
		359	Coro::on_enter {
		360	$old_tz = $ENV{TZ}; # remember the old value
		361
		362	$ENV{TZ} = "Antarctica/South_Pole";
		363	tzset; # enable new value
		364	};
		365
		366	Coro::on_leave {
		367	$ENV{TZ} = $old_tz;
		368	tzset; # restore old value
		369	};
		370
		371	# at this place, the timezone is Antarctica/South_Pole,
		372	# without disturbing the TZ of any other coro.
		373	};
		374
		375	This can be used to localise about any resource (locale, uid, current
		376	working directory etc.) to a block, despite the existance of other
		377	coros.
		378
		379	Another interesting example implements time-sliced multitasking using
		380	interval timers (this could obviously be optimised, but does the job):
		381
		382	# "timeslice" the given block
		383	sub timeslice(&) {
		384	use Time::HiRes ();
		385
		386	Coro::on_enter {
		387	# on entering the thread, we set an VTALRM handler to cede
		388	$SIG{VTALRM} = sub { cede };
		389	# and then start the interval timer
		390	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		391	};
		392	Coro::on_leave {
		393	# on leaving the thread, we stop the interval timer again
		394	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		395	};
		396
		397	&{+shift};
		398	}
		399
		400	# use like this:
		401	timeslice {
		402	# The following is an endless loop that would normally
		403	# monopolise the process. Sicne it runs in a timeslice
		404	# environment, it will regularly cede to other threads.
		405	while () { }
		406	};
		407
		408
		409	=item killall
		410
		411	Kills/terminates/cancels all coros except the currently running one.
		412
		413	Note that while this will try to free some of the main interpreter
		414	resources if the calling coro isn't the main coro, but one
		415	cannot free all of them, so if a coro that is not the main coro
		416	calls this function, there will be some one-time resource leak.
		417
		418	=cut
		419
		420	sub killall {
		421	for (Coro::State::list) {
		422	$_->cancel
		423	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		424	}
180	}	425	}
181		426
182	=back	427	=back
183		428
184	# dynamic methods	429	=head1 CORO OBJECT METHODS
185		430
186	=head2 PROCESS METHODS
187
188	These are the methods you can call on process objects.	431	These are the methods you can call on coro objects (or to create
		432	them).
189		433
190	=over 4	434	=over 4
191		435
192	=item new Coro \&sub [, @args...]	436	=item new Coro \&sub [, @args...]
193		437
194	Create a new process and return it. When the sub returns the process	438	Create a new coro and return it. When the sub returns, the coro
195	automatically terminates. To start the process you must first put it into	439	automatically terminates as if C<terminate> with the returned values were
		440	called. To make the coro run you must first put it into the ready
196	the ready queue by calling the ready method.	441	queue by calling the ready method.
197		442
198	The coderef you submit MUST NOT be a closure that refers to variables	443	See C<async> and C<Coro::State::new> for additional info about the
199	in an outer scope. This does NOT work. Pass arguments into it instead.	444	coro environment.
200		445
201	=cut	446	=cut
202		447
203	sub _newcoro {	448	sub _coro_run {
204	terminate &{+shift};	449	terminate &{+shift};
205	}	450	}
206		451
		452	=item $success = $coro->ready
		453
		454	Put the given coro into the end of its ready queue (there is one
		455	queue for each priority) and return true. If the coro is already in
		456	the ready queue, do nothing and return false.
		457
		458	This ensures that the scheduler will resume this coro automatically
		459	once all the coro of higher priority and all coro of the same
		460	priority that were put into the ready queue earlier have been resumed.
		461
		462	=item $coro->suspend
		463
		464	Suspends the specified coro. A suspended coro works just like any other
		465	coro, except that the scheduler will not select a suspended coro for
		466	execution.
		467
		468	Suspending a coro can be useful when you want to keep the coro from
		469	running, but you don't want to destroy it, or when you want to temporarily
		470	freeze a coro (e.g. for debugging) to resume it later.
		471
		472	A scenario for the former would be to suspend all (other) coros after a
		473	fork and keep them alive, so their destructors aren't called, but new
		474	coros can be created.
		475
		476	=item $coro->resume
		477
		478	If the specified coro was suspended, it will be resumed. Note that when
		479	the coro was in the ready queue when it was suspended, it might have been
		480	unreadied by the scheduler, so an activation might have been lost.
		481
		482	To avoid this, it is best to put a suspended coro into the ready queue
		483	unconditionally, as every synchronisation mechanism must protect itself
		484	against spurious wakeups, and the one in the Coro family certainly do
		485	that.
		486
		487	=item $is_ready = $coro->is_ready
		488
		489	Returns true iff the Coro object is in the ready queue. Unless the Coro
		490	object gets destroyed, it will eventually be scheduled by the scheduler.
		491
		492	=item $is_running = $coro->is_running
		493
		494	Returns true iff the Coro object is currently running. Only one Coro object
		495	can ever be in the running state (but it currently is possible to have
		496	multiple running Coro::States).
		497
		498	=item $is_suspended = $coro->is_suspended
		499
		500	Returns true iff this Coro object has been suspended. Suspended Coros will
		501	not ever be scheduled.
		502
		503	=item $coro->cancel (arg...)
		504
		505	Terminates the given Coro and makes it return the given arguments as
		506	status (default: the empty list). Never returns if the Coro is the
		507	current Coro.
		508
		509	=cut
		510
207	sub new {	511	sub cancel {
208	my $class = shift;	512	my $self = shift;
209	bless {
210	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
211	}, $class;
212	}
213		513
214	=item $process->ready	514	if ($current == $self) {
		515	terminate @_;
		516	} else {
		517	$self->{_status} = [@_];
		518	Coro::State::cancel $self;
		519	}
		520	}
215		521
216	Put the current process into the ready queue.	522	=item $coro->schedule_to
217		523
218	=cut	524	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		525	of continuing with the next coro from the ready queue, always switch to
		526	the given coro object (regardless of priority etc.). The readyness
		527	state of that coro isn't changed.
219		528
220	sub ready {	529	This is an advanced method for special cases - I'd love to hear about any
221	push @ready, $_[0];	530	uses for this one.
		531
		532	=item $coro->cede_to
		533
		534	Like C<schedule_to>, but puts the current coro into the ready
		535	queue. This has the effect of temporarily switching to the given
		536	coro, and continuing some time later.
		537
		538	This is an advanced method for special cases - I'd love to hear about any
		539	uses for this one.
		540
		541	=item $coro->throw ([$scalar])
		542
		543	If C<$throw> is specified and defined, it will be thrown as an exception
		544	inside the coro at the next convenient point in time. Otherwise
		545	clears the exception object.
		546
		547	Coro will check for the exception each time a schedule-like-function
		548	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		549	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		550	detect this case and return early in case an exception is pending.
		551
		552	The exception object will be thrown "as is" with the specified scalar in
		553	C<$@>, i.e. if it is a string, no line number or newline will be appended
		554	(unlike with C<die>).
		555
		556	This can be used as a softer means than C<cancel> to ask a coro to
		557	end itself, although there is no guarantee that the exception will lead to
		558	termination, and if the exception isn't caught it might well end the whole
		559	program.
		560
		561	You might also think of C<throw> as being the moral equivalent of
		562	C<kill>ing a coro with a signal (in this case, a scalar).
		563
		564	=item $coro->join
		565
		566	Wait until the coro terminates and return any values given to the
		567	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		568	from multiple coro, and all will be resumed and given the status
		569	return once the C<$coro> terminates.
		570
		571	=cut
		572
		573	sub join {
		574	my $self = shift;
		575
		576	unless ($self->{_status}) {
		577	my $current = $current;
		578
		579	push @{$self->{_on_destroy}}, sub {
		580	$current->ready;
		581	undef $current;
		582	};
		583
		584	&schedule while $current;
		585	}
		586
		587	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		588	}
		589
		590	=item $coro->on_destroy (\&cb)
		591
		592	Registers a callback that is called when this coro gets destroyed,
		593	but before it is joined. The callback gets passed the terminate arguments,
		594	if any, and I<must not> die, under any circumstances.
		595
		596	=cut
		597
		598	sub on_destroy {
		599	my ($self, $cb) = @_;
		600
		601	push @{ $self->{_on_destroy} }, $cb;
		602	}
		603
		604	=item $oldprio = $coro->prio ($newprio)
		605
		606	Sets (or gets, if the argument is missing) the priority of the
		607	coro. Higher priority coro get run before lower priority
		608	coro. Priorities are small signed integers (currently -4 .. +3),
		609	that you can refer to using PRIO_xxx constants (use the import tag :prio
		610	to get then):
		611
		612	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		613	3 > 1 > 0 > -1 > -3 > -4
		614
		615	# set priority to HIGH
		616	current->prio (PRIO_HIGH);
		617
		618	The idle coro ($Coro::idle) always has a lower priority than any
		619	existing coro.
		620
		621	Changing the priority of the current coro will take effect immediately,
		622	but changing the priority of coro in the ready queue (but not
		623	running) will only take effect after the next schedule (of that
		624	coro). This is a bug that will be fixed in some future version.
		625
		626	=item $newprio = $coro->nice ($change)
		627
		628	Similar to C<prio>, but subtract the given value from the priority (i.e.
		629	higher values mean lower priority, just as in unix).
		630
		631	=item $olddesc = $coro->desc ($newdesc)
		632
		633	Sets (or gets in case the argument is missing) the description for this
		634	coro. This is just a free-form string you can associate with a
		635	coro.
		636
		637	This method simply sets the C<< $coro->{desc} >> member to the given
		638	string. You can modify this member directly if you wish.
		639
		640	=cut
		641
		642	sub desc {
		643	my $old = $_[0]{desc};
		644	$_[0]{desc} = $_[1] if @_ > 1;
		645	$old;
		646	}
		647
		648	sub transfer {
		649	require Carp;
		650	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
222	}	651	}
223		652
224	=back	653	=back
225		654
		655	=head1 GLOBAL FUNCTIONS
		656
		657	=over 4
		658
		659	=item Coro::nready
		660
		661	Returns the number of coro that are currently in the ready state,
		662	i.e. that can be switched to by calling C<schedule> directory or
		663	indirectly. The value C<0> means that the only runnable coro is the
		664	currently running one, so C<cede> would have no effect, and C<schedule>
		665	would cause a deadlock unless there is an idle handler that wakes up some
		666	coro.
		667
		668	=item my $guard = Coro::guard { ... }
		669
		670	This function still exists, but is deprecated. Please use the
		671	C<Guard::guard> function instead.
		672
		673	=cut
		674
		675	BEGIN { *guard = \&Guard::guard }
		676
		677	=item unblock_sub { ... }
		678
		679	This utility function takes a BLOCK or code reference and "unblocks" it,
		680	returning a new coderef. Unblocking means that calling the new coderef
		681	will return immediately without blocking, returning nothing, while the
		682	original code ref will be called (with parameters) from within another
		683	coro.
		684
		685	The reason this function exists is that many event libraries (such as the
		686	venerable L<Event\|Event> module) are not thread-safe (a weaker form
		687	of reentrancy). This means you must not block within event callbacks,
		688	otherwise you might suffer from crashes or worse. The only event library
		689	currently known that is safe to use without C<unblock_sub> is L<EV>.
		690
		691	This function allows your callbacks to block by executing them in another
		692	coro where it is safe to block. One example where blocking is handy
		693	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		694	disk, for example.
		695
		696	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		697	creating event callbacks that want to block.
		698
		699	If your handler does not plan to block (e.g. simply sends a message to
		700	another coro, or puts some other coro into the ready queue), there is
		701	no reason to use C<unblock_sub>.
		702
		703	Note that you also need to use C<unblock_sub> for any other callbacks that
		704	are indirectly executed by any C-based event loop. For example, when you
		705	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		706	provides callbacks that are the result of some event callback, then you
		707	must not block either, or use C<unblock_sub>.
		708
		709	=cut
		710
		711	our @unblock_queue;
		712
		713	# we create a special coro because we want to cede,
		714	# to reduce pressure on the coro pool (because most callbacks
		715	# return immediately and can be reused) and because we cannot cede
		716	# inside an event callback.
		717	our $unblock_scheduler = new Coro sub {
		718	while () {
		719	while (my $cb = pop @unblock_queue) {
		720	&async_pool (@$cb);
		721
		722	# for short-lived callbacks, this reduces pressure on the coro pool
		723	# as the chance is very high that the async_poll coro will be back
		724	# in the idle state when cede returns
		725	cede;
		726	}
		727	schedule; # sleep well
		728	}
		729	};
		730	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
		731
		732	sub unblock_sub(&) {
		733	my $cb = shift;
		734
		735	sub {
		736	unshift @unblock_queue, [$cb, @_];
		737	$unblock_scheduler->ready;
		738	}
		739	}
		740
		741	=item $cb = Coro::rouse_cb
		742
		743	Create and return a "rouse callback". That's a code reference that,
		744	when called, will remember a copy of its arguments and notify the owner
		745	coro of the callback.
		746
		747	See the next function.
		748
		749	=item @args = Coro::rouse_wait [$cb]
		750
		751	Wait for the specified rouse callback (or the last one that was created in
		752	this coro).
		753
		754	As soon as the callback is invoked (or when the callback was invoked
		755	before C<rouse_wait>), it will return the arguments originally passed to
		756	the rouse callback.
		757
		758	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		759
		760	=back
		761
226	=cut	762	=cut
227		763
228	1;	764	1;
229		765
		766	=head1 HOW TO WAIT FOR A CALLBACK
		767
		768	It is very common for a coro to wait for some callback to be
		769	called. This occurs naturally when you use coro in an otherwise
		770	event-based program, or when you use event-based libraries.
		771
		772	These typically register a callback for some event, and call that callback
		773	when the event occured. In a coro, however, you typically want to
		774	just wait for the event, simplyifying things.
		775
		776	For example C<< AnyEvent->child >> registers a callback to be called when
		777	a specific child has exited:
		778
		779	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		780
		781	But from within a coro, you often just want to write this:
		782
		783	my $status = wait_for_child $pid;
		784
		785	Coro offers two functions specifically designed to make this easy,
		786	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		787
		788	The first function, C<rouse_cb>, generates and returns a callback that,
		789	when invoked, will save its arguments and notify the coro that
		790	created the callback.
		791
		792	The second function, C<rouse_wait>, waits for the callback to be called
		793	(by calling C<schedule> to go to sleep) and returns the arguments
		794	originally passed to the callback.
		795
		796	Using these functions, it becomes easy to write the C<wait_for_child>
		797	function mentioned above:
		798
		799	sub wait_for_child($) {
		800	my ($pid) = @_;
		801
		802	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		803
		804	my ($rpid, $rstatus) = Coro::rouse_wait;
		805	$rstatus
		806	}
		807
		808	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		809	you can roll your own, using C<schedule>:
		810
		811	sub wait_for_child($) {
		812	my ($pid) = @_;
		813
		814	# store the current coro in $current,
		815	# and provide result variables for the closure passed to ->child
		816	my $current = $Coro::current;
		817	my ($done, $rstatus);
		818
		819	# pass a closure to ->child
		820	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		821	$rstatus = $_[1]; # remember rstatus
		822	$done = 1; # mark $rstatus as valud
		823	});
		824
		825	# wait until the closure has been called
		826	schedule while !$done;
		827
		828	$rstatus
		829	}
		830
		831
230	=head1 BUGS/LIMITATIONS	832	=head1 BUGS/LIMITATIONS
231		833
232	- could be faster, especially when the core would introduce special	834	=over 4
233	support for coroutines (like it does for threads).	835
234	- there is still a memleak on coroutine termination that I could not	836	=item fork with pthread backend
235	identify. Could be as small as a single SV.	837
236	- this module is not well-tested.	838	When Coro is compiled using the pthread backend (which isn't recommended
237	- if variables or arguments "disappear" (become undef) or become	839	but required on many BSDs as their libcs are completely broken), then
238	corrupted please contact the author so he cen iron out the	840	coro will not survive a fork. There is no known workaround except to
239	remaining bugs.	841	fix your libc and use a saner backend.
240	- this module is not thread-safe. You must only ever use this module from	842
241	the same thread (this requirement might be loosened in the future to	843	=item perl process emulation ("threads")
		844
		845	This module is not perl-pseudo-thread-safe. You should only ever use this
		846	module from the first thread (this requirement might be removed in the
242	allow per-thread schedulers, but Coro::State does not yet allow this).	847	future to allow per-thread schedulers, but Coro::State does not yet allow
		848	this). I recommend disabling thread support and using processes, as having
		849	the windows process emulation enabled under unix roughly halves perl
		850	performance, even when not used.
		851
		852	=item coro switching is not signal safe
		853
		854	You must not switch to another coro from within a signal handler
		855	(only relevant with %SIG - most event libraries provide safe signals).
		856
		857	That means you I<MUST NOT> call any function that might "block" the
		858	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		859	anything that calls those. Everything else, including calling C<ready>,
		860	works.
		861
		862	=back
		863
243		864
244	=head1 SEE ALSO	865	=head1 SEE ALSO
245		866
246	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	867	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
247	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>.	868
		869	Debugging: L<Coro::Debug>.
		870
		871	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		872
		873	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		874	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		875
		876	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		877
		878	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		879	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		880	L<Coro::Select>.
		881
		882	XS API: L<Coro::MakeMaker>.
		883
		884	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
248		885
249	=head1 AUTHOR	886	=head1 AUTHOR
250		887
251	Marc Lehmann <pcg@goof.com>	888	Marc Lehmann <schmorp@schmorp.de>
252	http://www.goof.com/pcg/marc/	889	http://home.schmorp.de/
253		890
254	=cut	891	=cut
255		892

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Revision 1.255 by root, Wed Jun 17 21:36:35 2009 UTC