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

Comparing Coro/Coro.pm (file contents):
Revision 1.29 by root, Sat Aug 11 00:37:31 2001 UTC vs.
Revision 1.248 by root, Mon Dec 15 15:03:31 2008 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	cede;	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), Coro provides a
		46	full shared address space, which makes communication between threads
		47	very easy. And threads are fast, too: disabling the Windows process
		48	emulation code in your perl and using Coro can easily result in a two to
		49	four times speed increase for your programs.
		50
		51	Coro achieves that by supporting multiple running interpreters that share
		52	data, which is especially useful to code pseudo-parallel processes and
		53	for event-based programming, such as multiple HTTP-GET requests running
		54	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		55	into an event-based environment.
		56
28	In this module, coroutines are defined as "callchain + lexical variables	57	In this module, a thread is defined as "callchain + lexical variables +
29	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own	58	@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,
30	callchain, it's own set of lexicals and it's own set of perl's most	59	its own set of lexicals and its own set of perls most important global
31	important global variables.	60	variables (see L<Coro::State> for more configuration and background info).
		61
		62	See also the C<SEE ALSO> section at the end of this document - the Coro
		63	module family is quite large.
32		64
33	=cut	65	=cut
34		66
35	package Coro;	67	package Coro;
36		68
		69	use strict qw(vars subs);
		70	no warnings "uninitialized";
		71
		72	use Guard ();
		73
37	use Coro::State;	74	use Coro::State;
38		75
39	use base Exporter;	76	use base qw(Coro::State Exporter);
40		77
41	$VERSION = 0.45;	78	our $idle; # idle handler
		79	our $main; # main coro
		80	our $current; # current coro
42		81
		82	our $VERSION = 5.13;
		83
43	@EXPORT = qw(async cede schedule terminate current);	84	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44	@EXPORT_OK = qw($current);	85	our %EXPORT_TAGS = (
		86	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		87	);
		88	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
45		89
46	{	90	=head1 GLOBAL VARIABLES
47	my @async;
48	my $init;
49		91
50	# this way of handling attributes simply is NOT scalable ;()	92	=over 4
51	sub import {
52	Coro->export_to_level(1, @_);
53	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
54	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
55	my ($package, $ref) = (shift, shift);
56	my @attrs;
57	for (@_) {
58	if ($_ eq "Coro") {
59	push @async, $ref;
60	unless ($init++) {
61	eval q{
62	sub INIT {
63	&async(pop @async) while @async;
64	}
65	};
66	}
67	} else {
68	push @attrs, $_;
69	}
70	}
71	return $old ? $old->($package, $ref, @attrs) : @attrs;
72	};
73	}
74		93
75	}
76
77	=item $main	94	=item $Coro::main
78		95
79	This coroutine represents the main program.	96	This variable stores the Coro object that represents the main
		97	program. While you cna C<ready> it and do most other things you can do to
		98	coro, it is mainly useful to compare again C<$Coro::current>, to see
		99	whether you are running in the main program or not.
80		100
81	=cut	101	=cut
82		102
83	our $main = new Coro;	103	# $main is now being initialised by Coro::State
84		104
85	=item $current (or as function: current)	105	=item $Coro::current
86		106
87	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	107	The Coro object representing the current coro (the last
		108	coro that the Coro scheduler switched to). The initial value is
		109	C<$Coro::main> (of course).
88		110
89	=cut	111	This variable is B<strictly> I<read-only>. You can take copies of the
		112	value stored in it and use it as any other Coro object, but you must
		113	not otherwise modify the variable itself.
90		114
91	# maybe some other module used Coro::Specific before...	115	=cut
92	if ($current) {
93	$main->{specific} = $current->{specific};
94	}
95		116
96	our $current = $main;
97
98	sub current() { $current }	117	sub current() { $current } # [DEPRECATED]
99		118
100	=item $idle	119	=item $Coro::idle
101		120
102	The coroutine to switch to when no other coroutine is running. The default	121	This variable is mainly useful to integrate Coro into event loops. It is
103	implementation prints "FATAL: deadlock detected" and exits.	122	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		123	pretty low-level functionality.
104		124
105	=cut	125	This variable stores either a Coro object or a callback.
106		126
107	# should be done using priorities :(	127	If it is a callback, the it is called whenever the scheduler finds no
108	our $idle = new Coro sub {	128	ready coros to run. The default implementation prints "FATAL:
109	print STDERR "FATAL: deadlock detected\n";	129	deadlock detected" and exits, because the program has no other way to
110	exit(51);	130	continue.
		131
		132	If it is a coro object, then this object will be readied (without
		133	invoking any ready hooks, however) when the scheduler finds no other ready
		134	coros to run.
		135
		136	This hook is overwritten by modules such as C<Coro::EV> and
		137	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
		138	coro so the scheduler can run it.
		139
		140	Note that the callback I<must not>, under any circumstances, block
		141	the current coro. Normally, this is achieved by having an "idle
		142	coro" that calls the event loop and then blocks again, and then
		143	readying that coro in the idle handler, or by simply placing the idle
		144	coro in this variable.
		145
		146	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		147	technique.
		148
		149	Please note that if your callback recursively invokes perl (e.g. for event
		150	handlers), then it must be prepared to be called recursively itself.
		151
		152	=cut
		153
		154	$idle = sub {
		155	require Carp;
		156	Carp::croak ("FATAL: deadlock detected");
111	};	157	};
112		158
113	# this coroutine is necessary because a coroutine	159	# this coro is necessary because a coro
114	# cannot destroy itself.	160	# cannot destroy itself.
115	my @destroy;	161	our @destroy;
		162	our $manager;
		163
116	my $manager = new Coro sub {	164	$manager = new Coro sub {
117	while() {	165	while () {
118	delete ((pop @destroy)->{_coro_state}) while @destroy;	166	Coro::State::cancel shift @destroy
		167	while @destroy;
		168
119	&schedule;	169	&schedule;
120	}	170	}
121	};	171	};
		172	$manager->{desc} = "[coro manager]";
		173	$manager->prio (PRIO_MAX);
122		174
123	# we really need priorities...	175	=back
124	my @ready; # the ready queue. hehe, rather broken ;)
125		176
126	# static methods. not really.	177	=head1 SIMPLE CORO CREATION
127
128	=head2 STATIC METHODS
129
130	Static methods are actually functions that operate on the current process only.
131		178
132	=over 4	179	=over 4
133		180
134	=item async { ... } [@args...]	181	=item async { ... } [@args...]
135		182
136	Create a new asynchronous process and return it's process object	183	Create a new coro and return its Coro object (usually
137	(usually unused). When the sub returns the new process is automatically	184	unused). The coro will be put into the ready queue, so
		185	it will start running automatically on the next scheduler run.
		186
		187	The first argument is a codeblock/closure that should be executed in the
		188	coro. When it returns argument returns the coro is automatically
138	terminated.	189	terminated.
139		190
		191	The remaining arguments are passed as arguments to the closure.
		192
		193	See the C<Coro::State::new> constructor for info about the coro
		194	environment in which coro are executed.
		195
		196	Calling C<exit> in a coro will do the same as calling exit outside
		197	the coro. Likewise, when the coro dies, the program will exit,
		198	just as it would in the main program.
		199
		200	If you do not want that, you can provide a default C<die> handler, or
		201	simply avoid dieing (by use of C<eval>).
		202
140	# create a new coroutine that just prints its arguments	203	Example: Create a new coro that just prints its arguments.
		204
141	async {	205	async {
142	print "@_\n";	206	print "@_\n";
143	} 1,2,3,4;	207	} 1,2,3,4;
144		208
145	The coderef you submit MUST NOT be a closure that refers to variables
146	in an outer scope. This does NOT work. Pass arguments into it instead.
147
148	=cut	209	=cut
149		210
150	sub async(&@) {	211	sub async(&@) {
151	my $pid = new Coro @_;	212	my $coro = new Coro @_;
152	$manager->ready; # this ensures that the stack is cloned from the manager
153	$pid->ready;	213	$coro->ready;
154	$pid;	214	$coro
155	}	215	}
		216
		217	=item async_pool { ... } [@args...]
		218
		219	Similar to C<async>, but uses a coro pool, so you should not call
		220	terminate or join on it (although you are allowed to), and you get a
		221	coro that might have executed other code already (which can be good
		222	or bad :).
		223
		224	On the plus side, this function is about twice as fast as creating (and
		225	destroying) a completely new coro, so if you need a lot of generic
		226	coros in quick successsion, use C<async_pool>, not C<async>.
		227
		228	The code block is executed in an C<eval> context and a warning will be
		229	issued in case of an exception instead of terminating the program, as
		230	C<async> does. As the coro is being reused, stuff like C<on_destroy>
		231	will not work in the expected way, unless you call terminate or cancel,
		232	which somehow defeats the purpose of pooling (but is fine in the
		233	exceptional case).
		234
		235	The priority will be reset to C<0> after each run, tracing will be
		236	disabled, the description will be reset and the default output filehandle
		237	gets restored, so you can change all these. Otherwise the coro will
		238	be re-used "as-is": most notably if you change other per-coro global
		239	stuff such as C<$/> you I<must needs> revert that change, which is most
		240	simply done by using local as in: C<< local $/ >>.
		241
		242	The idle pool size is limited to C<8> idle coros (this can be
		243	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		244	coros as required.
		245
		246	If you are concerned about pooled coros growing a lot because a
		247	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		248	{ terminate }> once per second or so to slowly replenish the pool. In
		249	addition to that, when the stacks used by a handler grows larger than 32kb
		250	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		251
		252	=cut
		253
		254	our $POOL_SIZE = 8;
		255	our $POOL_RSS = 32 * 1024;
		256	our @async_pool;
		257
		258	sub pool_handler {
		259	while () {
		260	eval {
		261	&{&_pool_handler} while 1;
		262	};
		263
		264	warn $@ if $@;
		265	}
		266	}
		267
		268	=back
		269
		270	=head1 STATIC METHODS
		271
		272	Static methods are actually functions that implicitly operate on the
		273	current coro.
		274
		275	=over 4
156		276
157	=item schedule	277	=item schedule
158		278
159	Calls the scheduler. Please note that the current process will not be put	279	Calls the scheduler. The scheduler will find the next coro that is
		280	to be run from the ready queue and switches to it. The next coro
		281	to be run is simply the one with the highest priority that is longest
		282	in its ready queue. If there is no coro ready, it will clal the
		283	C<$Coro::idle> hook.
		284
		285	Please note that the current coro will I<not> be put into the ready
160	into the ready queue, so calling this function usually means you will	286	queue, so calling this function usually means you will never be called
161	never be called again.	287	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		288	thus waking you up.
162		289
163	=cut	290	This makes C<schedule> I<the> generic method to use to block the current
		291	coro and wait for events: first you remember the current coro in
		292	a variable, then arrange for some callback of yours to call C<< ->ready
		293	>> on that once some event happens, and last you call C<schedule> to put
		294	yourself to sleep. Note that a lot of things can wake your coro up,
		295	so you need to check whether the event indeed happened, e.g. by storing the
		296	status in a variable.
164		297
165	my $prev;	298	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
166
167	sub schedule {
168	# should be done using priorities :(
169	($prev, $current) = ($current, shift @ready \|\| $idle);
170	Coro::State::transfer($prev, $current);
171	}
172		299
173	=item cede	300	=item cede
174		301
175	"Cede" to other processes. This function puts the current process into the	302	"Cede" to other coros. This function puts the current coro into
176	ready queue and calls C<schedule>, which has the effect of giving up the	303	the ready queue and calls C<schedule>, which has the effect of giving
177	current "timeslice" to other coroutines of the same or higher priority.	304	up the current "timeslice" to other coros of the same or higher
		305	priority. Once your coro gets its turn again it will automatically be
		306	resumed.
178		307
179	=cut	308	This function is often called C<yield> in other languages.
180		309
181	sub cede {	310	=item Coro::cede_notself
182	$current->ready;
183	&schedule;
184	}
185		311
		312	Works like cede, but is not exported by default and will cede to I<any>
		313	coro, regardless of priority. This is useful sometimes to ensure
		314	progress is made.
		315
186	=item terminate	316	=item terminate [arg...]
187		317
188	Terminates the current process.	318	Terminates the current coro with the given status values (see L<cancel>).
189		319
190	Future versions of this function will allow result arguments.	320	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
191		321
192	=cut	322	These function install enter and leave winders in the current scope. The
		323	enter block will be executed when on_enter is called and whenever the
		324	current coro is re-entered by the scheduler, while the leave block is
		325	executed whenever the current coro is blocked by the scheduler, and
		326	also when the containing scope is exited (by whatever means, be it exit,
		327	die, last etc.).
193		328
194	sub terminate {	329	I<Neither invoking the scheduler, nor exceptions, are allowed within those
195	$current->cancel;	330	BLOCKs>. That means: do not even think about calling C<die> without an
196	&schedule;	331	eval, and do not even think of entering the scheduler in any way.
197	die; # NORETURN	332
		333	Since both BLOCKs are tied to the current scope, they will automatically
		334	be removed when the current scope exits.
		335
		336	These functions implement the same concept as C<dynamic-wind> in scheme
		337	does, and are useful when you want to localise some resource to a specific
		338	coro.
		339
		340	They slow down coro switching considerably for coros that use
		341	them (But coro switching is still reasonably fast if the handlers are
		342	fast).
		343
		344	These functions are best understood by an example: The following function
		345	will change the current timezone to "Antarctica/South_Pole", which
		346	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		347	which remember/change the current timezone and restore the previous
		348	value, respectively, the timezone is only changes for the coro that
		349	installed those handlers.
		350
		351	use POSIX qw(tzset);
		352
		353	async {
		354	my $old_tz; # store outside TZ value here
		355
		356	Coro::on_enter {
		357	$old_tz = $ENV{TZ}; # remember the old value
		358
		359	$ENV{TZ} = "Antarctica/South_Pole";
		360	tzset; # enable new value
		361	};
		362
		363	Coro::on_leave {
		364	$ENV{TZ} = $old_tz;
		365	tzset; # restore old value
		366	};
		367
		368	# at this place, the timezone is Antarctica/South_Pole,
		369	# without disturbing the TZ of any other coro.
		370	};
		371
		372	This can be used to localise about any resource (locale, uid, current
		373	working directory etc.) to a block, despite the existance of other
		374	coros.
		375
		376	=item killall
		377
		378	Kills/terminates/cancels all coros except the currently running one.
		379
		380	Note that while this will try to free some of the main interpreter
		381	resources if the calling coro isn't the main coro, but one
		382	cannot free all of them, so if a coro that is not the main coro
		383	calls this function, there will be some one-time resource leak.
		384
		385	=cut
		386
		387	sub killall {
		388	for (Coro::State::list) {
		389	$_->cancel
		390	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		391	}
198	}	392	}
199		393
200	=back	394	=back
201		395
202	# dynamic methods	396	=head1 CORO OBJECT METHODS
203		397
204	=head2 PROCESS METHODS
205
206	These are the methods you can call on process objects.	398	These are the methods you can call on coro objects (or to create
		399	them).
207		400
208	=over 4	401	=over 4
209		402
210	=item new Coro \&sub [, @args...]	403	=item new Coro \&sub [, @args...]
211		404
212	Create a new process and return it. When the sub returns the process	405	Create a new coro and return it. When the sub returns, the coro
213	automatically terminates. To start the process you must first put it into	406	automatically terminates as if C<terminate> with the returned values were
		407	called. To make the coro run you must first put it into the ready
214	the ready queue by calling the ready method.	408	queue by calling the ready method.
215		409
216	The coderef you submit MUST NOT be a closure that refers to variables	410	See C<async> and C<Coro::State::new> for additional info about the
217	in an outer scope. This does NOT work. Pass arguments into it instead.	411	coro environment.
218		412
219	=cut	413	=cut
220		414
221	sub _newcoro {	415	sub _coro_run {
222	terminate &{+shift};	416	terminate &{+shift};
223	}	417	}
224		418
225	sub new {	419	=item $success = $coro->ready
226	my $class = shift;
227	bless {
228	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229	}, $class;
230	}
231		420
232	=item $process->ready	421	Put the given coro into the end of its ready queue (there is one
		422	queue for each priority) and return true. If the coro is already in
		423	the ready queue, do nothing and return false.
233		424
234	Put the current process into the ready queue.	425	This ensures that the scheduler will resume this coro automatically
		426	once all the coro of higher priority and all coro of the same
		427	priority that were put into the ready queue earlier have been resumed.
235		428
236	=cut	429	=item $is_ready = $coro->is_ready
237		430
238	sub ready {	431	Returns true iff the Coro object is in the ready queue. Unless the Coro
239	push @ready, $_[0];	432	object gets destroyed, it will eventually be scheduled by the scheduler.
240	}
241		433
242	=item $process->cancel	434	=item $is_running = $coro->is_running
243		435
244	Like C<terminate>, but terminates the specified process instead.	436	Returns true iff the Coro object is currently running. Only one Coro object
		437	can ever be in the running state (but it currently is possible to have
		438	multiple running Coro::States).
		439
		440	=item $is_suspended = $coro->is_suspended
		441
		442	Returns true iff this Coro object has been suspended. Suspended Coros will
		443	not ever be scheduled.
		444
		445	=item $coro->cancel (arg...)
		446
		447	Terminates the given Coro and makes it return the given arguments as
		448	status (default: the empty list). Never returns if the Coro is the
		449	current Coro.
245		450
246	=cut	451	=cut
247		452
248	sub cancel {	453	sub cancel {
249	push @destroy, $_[0];	454	my $self = shift;
250	$manager->ready;	455
		456	if ($current == $self) {
		457	terminate @_;
		458	} else {
		459	$self->{_status} = [@_];
		460	Coro::State::cancel $self;
		461	}
		462	}
		463
		464	=item $coro->schedule_to
		465
		466	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		467	of continuing with the next coro from the ready queue, always switch to
		468	the given coro object (regardless of priority etc.). The readyness
		469	state of that coro isn't changed.
		470
		471	This is an advanced method for special cases - I'd love to hear about any
		472	uses for this one.
		473
		474	=item $coro->cede_to
		475
		476	Like C<schedule_to>, but puts the current coro into the ready
		477	queue. This has the effect of temporarily switching to the given
		478	coro, and continuing some time later.
		479
		480	This is an advanced method for special cases - I'd love to hear about any
		481	uses for this one.
		482
		483	=item $coro->throw ([$scalar])
		484
		485	If C<$throw> is specified and defined, it will be thrown as an exception
		486	inside the coro at the next convenient point in time. Otherwise
		487	clears the exception object.
		488
		489	Coro will check for the exception each time a schedule-like-function
		490	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		491	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		492	detect this case and return early in case an exception is pending.
		493
		494	The exception object will be thrown "as is" with the specified scalar in
		495	C<$@>, i.e. if it is a string, no line number or newline will be appended
		496	(unlike with C<die>).
		497
		498	This can be used as a softer means than C<cancel> to ask a coro to
		499	end itself, although there is no guarantee that the exception will lead to
		500	termination, and if the exception isn't caught it might well end the whole
		501	program.
		502
		503	You might also think of C<throw> as being the moral equivalent of
		504	C<kill>ing a coro with a signal (in this case, a scalar).
		505
		506	=item $coro->join
		507
		508	Wait until the coro terminates and return any values given to the
		509	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		510	from multiple coro, and all will be resumed and given the status
		511	return once the C<$coro> terminates.
		512
		513	=cut
		514
		515	sub join {
		516	my $self = shift;
		517
		518	unless ($self->{_status}) {
		519	my $current = $current;
		520
		521	push @{$self->{_on_destroy}}, sub {
		522	$current->ready;
		523	undef $current;
		524	};
		525
		526	&schedule while $current;
		527	}
		528
		529	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		530	}
		531
		532	=item $coro->on_destroy (\&cb)
		533
		534	Registers a callback that is called when this coro gets destroyed,
		535	but before it is joined. The callback gets passed the terminate arguments,
		536	if any, and I<must not> die, under any circumstances.
		537
		538	=cut
		539
		540	sub on_destroy {
		541	my ($self, $cb) = @_;
		542
		543	push @{ $self->{_on_destroy} }, $cb;
		544	}
		545
		546	=item $oldprio = $coro->prio ($newprio)
		547
		548	Sets (or gets, if the argument is missing) the priority of the
		549	coro. Higher priority coro get run before lower priority
		550	coro. Priorities are small signed integers (currently -4 .. +3),
		551	that you can refer to using PRIO_xxx constants (use the import tag :prio
		552	to get then):
		553
		554	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		555	3 > 1 > 0 > -1 > -3 > -4
		556
		557	# set priority to HIGH
		558	current->prio (PRIO_HIGH);
		559
		560	The idle coro ($Coro::idle) always has a lower priority than any
		561	existing coro.
		562
		563	Changing the priority of the current coro will take effect immediately,
		564	but changing the priority of coro in the ready queue (but not
		565	running) will only take effect after the next schedule (of that
		566	coro). This is a bug that will be fixed in some future version.
		567
		568	=item $newprio = $coro->nice ($change)
		569
		570	Similar to C<prio>, but subtract the given value from the priority (i.e.
		571	higher values mean lower priority, just as in unix).
		572
		573	=item $olddesc = $coro->desc ($newdesc)
		574
		575	Sets (or gets in case the argument is missing) the description for this
		576	coro. This is just a free-form string you can associate with a
		577	coro.
		578
		579	This method simply sets the C<< $coro->{desc} >> member to the given
		580	string. You can modify this member directly if you wish.
		581
		582	=cut
		583
		584	sub desc {
		585	my $old = $_[0]{desc};
		586	$_[0]{desc} = $_[1] if @_ > 1;
		587	$old;
		588	}
		589
		590	sub transfer {
		591	require Carp;
		592	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
251	}	593	}
252		594
253	=back	595	=back
254		596
		597	=head1 GLOBAL FUNCTIONS
		598
		599	=over 4
		600
		601	=item Coro::nready
		602
		603	Returns the number of coro that are currently in the ready state,
		604	i.e. that can be switched to by calling C<schedule> directory or
		605	indirectly. The value C<0> means that the only runnable coro is the
		606	currently running one, so C<cede> would have no effect, and C<schedule>
		607	would cause a deadlock unless there is an idle handler that wakes up some
		608	coro.
		609
		610	=item my $guard = Coro::guard { ... }
		611
		612	This function still exists, but is deprecated. Please use the
		613	C<Guard::guard> function instead.
		614
		615	=cut
		616
		617	BEGIN { *guard = \&Guard::guard }
		618
		619	=item unblock_sub { ... }
		620
		621	This utility function takes a BLOCK or code reference and "unblocks" it,
		622	returning a new coderef. Unblocking means that calling the new coderef
		623	will return immediately without blocking, returning nothing, while the
		624	original code ref will be called (with parameters) from within another
		625	coro.
		626
		627	The reason this function exists is that many event libraries (such as the
		628	venerable L<Event\|Event> module) are not thread-safe (a weaker form
		629	of reentrancy). This means you must not block within event callbacks,
		630	otherwise you might suffer from crashes or worse. The only event library
		631	currently known that is safe to use without C<unblock_sub> is L<EV>.
		632
		633	This function allows your callbacks to block by executing them in another
		634	coro where it is safe to block. One example where blocking is handy
		635	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		636	disk, for example.
		637
		638	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		639	creating event callbacks that want to block.
		640
		641	If your handler does not plan to block (e.g. simply sends a message to
		642	another coro, or puts some other coro into the ready queue), there is
		643	no reason to use C<unblock_sub>.
		644
		645	Note that you also need to use C<unblock_sub> for any other callbacks that
		646	are indirectly executed by any C-based event loop. For example, when you
		647	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		648	provides callbacks that are the result of some event callback, then you
		649	must not block either, or use C<unblock_sub>.
		650
		651	=cut
		652
		653	our @unblock_queue;
		654
		655	# we create a special coro because we want to cede,
		656	# to reduce pressure on the coro pool (because most callbacks
		657	# return immediately and can be reused) and because we cannot cede
		658	# inside an event callback.
		659	our $unblock_scheduler = new Coro sub {
		660	while () {
		661	while (my $cb = pop @unblock_queue) {
		662	&async_pool (@$cb);
		663
		664	# for short-lived callbacks, this reduces pressure on the coro pool
		665	# as the chance is very high that the async_poll coro will be back
		666	# in the idle state when cede returns
		667	cede;
		668	}
		669	schedule; # sleep well
		670	}
		671	};
		672	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
		673
		674	sub unblock_sub(&) {
		675	my $cb = shift;
		676
		677	sub {
		678	unshift @unblock_queue, [$cb, @_];
		679	$unblock_scheduler->ready;
		680	}
		681	}
		682
		683	=item $cb = Coro::rouse_cb
		684
		685	Create and return a "rouse callback". That's a code reference that,
		686	when called, will remember a copy of its arguments and notify the owner
		687	coro of the callback.
		688
		689	See the next function.
		690
		691	=item @args = Coro::rouse_wait [$cb]
		692
		693	Wait for the specified rouse callback (or the last one that was created in
		694	this coro).
		695
		696	As soon as the callback is invoked (or when the callback was invoked
		697	before C<rouse_wait>), it will return the arguments originally passed to
		698	the rouse callback.
		699
		700	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		701
		702	=back
		703
255	=cut	704	=cut
256		705
257	1;	706	1;
258		707
		708	=head1 HOW TO WAIT FOR A CALLBACK
		709
		710	It is very common for a coro to wait for some callback to be
		711	called. This occurs naturally when you use coro in an otherwise
		712	event-based program, or when you use event-based libraries.
		713
		714	These typically register a callback for some event, and call that callback
		715	when the event occured. In a coro, however, you typically want to
		716	just wait for the event, simplyifying things.
		717
		718	For example C<< AnyEvent->child >> registers a callback to be called when
		719	a specific child has exited:
		720
		721	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		722
		723	But from within a coro, you often just want to write this:
		724
		725	my $status = wait_for_child $pid;
		726
		727	Coro offers two functions specifically designed to make this easy,
		728	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		729
		730	The first function, C<rouse_cb>, generates and returns a callback that,
		731	when invoked, will save its arguments and notify the coro that
		732	created the callback.
		733
		734	The second function, C<rouse_wait>, waits for the callback to be called
		735	(by calling C<schedule> to go to sleep) and returns the arguments
		736	originally passed to the callback.
		737
		738	Using these functions, it becomes easy to write the C<wait_for_child>
		739	function mentioned above:
		740
		741	sub wait_for_child($) {
		742	my ($pid) = @_;
		743
		744	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		745
		746	my ($rpid, $rstatus) = Coro::rouse_wait;
		747	$rstatus
		748	}
		749
		750	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		751	you can roll your own, using C<schedule>:
		752
		753	sub wait_for_child($) {
		754	my ($pid) = @_;
		755
		756	# store the current coro in $current,
		757	# and provide result variables for the closure passed to ->child
		758	my $current = $Coro::current;
		759	my ($done, $rstatus);
		760
		761	# pass a closure to ->child
		762	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		763	$rstatus = $_[1]; # remember rstatus
		764	$done = 1; # mark $rstatus as valud
		765	});
		766
		767	# wait until the closure has been called
		768	schedule while !$done;
		769
		770	$rstatus
		771	}
		772
		773
259	=head1 BUGS/LIMITATIONS	774	=head1 BUGS/LIMITATIONS
260		775
261	- could be faster, especially when the core would introduce special	776	=over 4
262	support for coroutines (like it does for threads).	777
263	- there is still a memleak on coroutine termination that I could not	778	=item fork with pthread backend
264	identify. Could be as small as a single SV.	779
265	- this module is not well-tested.	780	When Coro is compiled using the pthread backend (which isn't recommended
266	- if variables or arguments "disappear" (become undef) or become	781	but required on many BSDs as their libcs are completely broken), then
267	corrupted please contact the author so he cen iron out the	782	coro will not survive a fork. There is no known workaround except to
268	remaining bugs.	783	fix your libc and use a saner backend.
269	- this module is not thread-safe. You must only ever use this module from	784
270	the same thread (this requirement might be loosened in the future to	785	=item perl process emulation ("threads")
		786
		787	This module is not perl-pseudo-thread-safe. You should only ever use this
		788	module from the first thread (this requirement might be removed in the
271	allow per-thread schedulers, but Coro::State does not yet allow this).	789	future to allow per-thread schedulers, but Coro::State does not yet allow
		790	this). I recommend disabling thread support and using processes, as having
		791	the windows process emulation enabled under unix roughly halves perl
		792	performance, even when not used.
		793
		794	=item coro switching is not signal safe
		795
		796	You must not switch to another coro from within a signal handler
		797	(only relevant with %SIG - most event libraries provide safe signals).
		798
		799	That means you I<MUST NOT> call any function that might "block" the
		800	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		801	anything that calls those. Everything else, including calling C<ready>,
		802	works.
		803
		804	=back
		805
272		806
273	=head1 SEE ALSO	807	=head1 SEE ALSO
274		808
275	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	809	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
276	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,	810
277	L<Coro::Handle>, L<Coro::Socket>.	811	Debugging: L<Coro::Debug>.
		812
		813	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		814
		815	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		816	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		817
		818	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		819
		820	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		821	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		822	L<Coro::Select>.
		823
		824	XS API: L<Coro::MakeMaker>.
		825
		826	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
278		827
279	=head1 AUTHOR	828	=head1 AUTHOR
280		829
281	Marc Lehmann <pcg@goof.com>	830	Marc Lehmann <schmorp@schmorp.de>
282	http://www.goof.com/pcg/marc/	831	http://home.schmorp.de/
283		832
284	=cut	833	=cut
285		834

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Revision 1.248 by root, Mon Dec 15 15:03:31 2008 UTC