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

Comparing Coro/Coro.pm (file contents):
Revision 1.132 by root, Thu Sep 20 22:53:23 2007 UTC vs.
Revision 1.244 by root, Sat Dec 13 22:08:13 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 coroutine like this:	16	cede; # yield to coroutine
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	31	For a tutorial-style introduction, please read the L<Coro::Intro>
24	to threads but don't run in parallel at the same time even on SMP	32	manpage. This manpage mainly contains reference information.
25	machines. The specific flavor of coroutine used in this module also
26	guarantees you that it will not switch between coroutines unless
27	necessary, at easily-identified points in your program, so locking and
28	parallel access are rarely an issue, making coroutine programming much
29	safer than threads programming.
30		33
31	(Perl, however, does not natively support real threads but instead does a	34	This module collection manages continuations in general, most often
32	very slow and memory-intensive emulation of processes using threads. This	35	in the form of cooperative threads (also called coroutines in the
33	is a performance win on Windows machines, and a loss everywhere else).	36	documentation). They are similar to kernel threads but don't (in general)
		37	run in parallel at the same time even on SMP machines. The specific flavor
		38	of thread offered by this module also guarantees you that it will not
		39	switch between threads unless necessary, at easily-identified points in
		40	your program, so locking and parallel access are rarely an issue, making
		41	thread programming much safer and easier than using other thread models.
34		42
		43	Unlike the so-called "Perl threads" (which are not actually real threads
		44	but only the windows process emulation ported to unix), Coro provides a
		45	full shared address space, which makes communication between threads
		46	very easy. And threads are fast, too: disabling the Windows process
		47	emulation code in your perl and using Coro can easily result in a two to
		48	four times speed increase for your programs.
		49
		50	Coro achieves that by supporting multiple running interpreters that share
		51	data, which is especially useful to code pseudo-parallel processes and
		52	for event-based programming, such as multiple HTTP-GET requests running
		53	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		54	into an event-based environment.
		55
35	In this module, coroutines are defined as "callchain + lexical variables +	56	In this module, a thread is defined as "callchain + lexical variables +
36	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	57	@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,
37	its own set of lexicals and its own set of perls most important global	58	its own set of lexicals and its own set of perls most important global
38	variables.	59	variables (see L<Coro::State> for more configuration and background info).
		60
		61	See also the C<SEE ALSO> section at the end of this document - the Coro
		62	module family is quite large.
39		63
40	=cut	64	=cut
41		65
42	package Coro;	66	package Coro;
43		67
44	use strict;	68	use strict qw(vars subs);
45	no warnings "uninitialized";	69	no warnings "uninitialized";
46		70
47	use Coro::State;	71	use Coro::State;
48		72
49	use base qw(Coro::State Exporter);	73	use base qw(Coro::State Exporter);
50		74
51	our $idle; # idle handler	75	our $idle; # idle handler
52	our $main; # main coroutine	76	our $main; # main coroutine
53	our $current; # current coroutine	77	our $current; # current coroutine
54		78
55	our $VERSION = '3.7';	79	our $VERSION = 5.13;
56		80
57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	81	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
58	our %EXPORT_TAGS = (	82	our %EXPORT_TAGS = (
59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	83	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60	);	84	);
61	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	85	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
62		86
63	{	87	=head1 GLOBAL VARIABLES
64	my @async;
65	my $init;
66
67	# this way of handling attributes simply is NOT scalable ;()
68	sub import {
69	no strict 'refs';
70
71	Coro->export_to_level (1, @_);
72
73	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
74	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
75	my ($package, $ref) = (shift, shift);
76	my @attrs;
77	for (@_) {
78	if ($_ eq "Coro") {
79	push @async, $ref;
80	unless ($init++) {
81	eval q{
82	sub INIT {
83	&async(pop @async) while @async;
84	}
85	};
86	}
87	} else {
88	push @attrs, $_;
89	}
90	}
91	return $old ? $old->($package, $ref, @attrs) : @attrs;
92	};
93	}
94
95	}
96		88
97	=over 4	89	=over 4
98		90
99	=item $main	91	=item $Coro::main
100		92
101	This coroutine represents the main program.	93	This variable stores the coroutine object that represents the main
		94	program. While you cna C<ready> it and do most other things you can do to
		95	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		96	whether you are running in the main program or not.
102		97
103	=cut	98	=cut
104		99
105	$main = new Coro;	100	# $main is now being initialised by Coro::State
106		101
107	=item $current (or as function: current)	102	=item $Coro::current
108		103
109	The current coroutine (the last coroutine switched to). The initial value	104	The coroutine object representing the current coroutine (the last
		105	coroutine that the Coro scheduler switched to). The initial value is
110	is C<$main> (of course).	106	C<$Coro::main> (of course).
111		107
112	This variable is B<strictly> I<read-only>. It is provided for performance	108	This variable is B<strictly> I<read-only>. You can take copies of the
113	reasons. If performance is not essential you are encouraged to use the	109	value stored in it and use it as any other coroutine object, but you must
114	C<Coro::current> function instead.	110	not otherwise modify the variable itself.
115		111
116	=cut	112	=cut
117		113
118	$main->{desc} = "[main::]";
119
120	# maybe some other module used Coro::Specific before...
121	$main->{specific} = $current->{specific}
122	if $current;
123
124	_set_current $main;
125
126	sub current() { $current }	114	sub current() { $current } # [DEPRECATED]
127		115
128	=item $idle	116	=item $Coro::idle
129		117
		118	This variable is mainly useful to integrate Coro into event loops. It is
		119	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		120	pretty low-level functionality.
		121
		122	This variable stores either a coroutine or a callback.
		123
130	A callback that is called whenever the scheduler finds no ready coroutines	124	If it is a callback, the it is called whenever the scheduler finds no
131	to run. The default implementation prints "FATAL: deadlock detected" and	125	ready coroutines to run. The default implementation prints "FATAL:
132	exits, because the program has no other way to continue.	126	deadlock detected" and exits, because the program has no other way to
		127	continue.
133		128
		129	If it is a coroutine object, then this object will be readied (without
		130	invoking any ready hooks, however) when the scheduler finds no other ready
		131	coroutines to run.
		132
134	This hook is overwritten by modules such as C<Coro::Timer> and	133	This hook is overwritten by modules such as C<Coro::EV> and
135	C<Coro::Event> to wait on an external event that hopefully wake up a	134	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
136	coroutine so the scheduler can run it.	135	coroutine so the scheduler can run it.
137		136
		137	Note that the callback I<must not>, under any circumstances, block
		138	the current coroutine. Normally, this is achieved by having an "idle
		139	coroutine" that calls the event loop and then blocks again, and then
		140	readying that coroutine in the idle handler, or by simply placing the idle
		141	coroutine in this variable.
		142
		143	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		144	technique.
		145
138	Please note that if your callback recursively invokes perl (e.g. for event	146	Please note that if your callback recursively invokes perl (e.g. for event
139	handlers), then it must be prepared to be called recursively.	147	handlers), then it must be prepared to be called recursively itself.
140		148
141	=cut	149	=cut
142		150
143	$idle = sub {	151	$idle = sub {
144	require Carp;	152	require Carp;
145	Carp::croak ("FATAL: deadlock detected");	153	Carp::croak ("FATAL: deadlock detected");
146	};	154	};
147		155
148	sub _cancel {
149	my ($self) = @_;
150
151	# free coroutine data and mark as destructed
152	$self->_destroy
153	or return;
154
155	# call all destruction callbacks
156	$_->(@{$self->{status}})
157	for @{(delete $self->{destroy_cb}) \|\| []};
158	}
159
160	# this coroutine is necessary because a coroutine	156	# this coroutine is necessary because a coroutine
161	# cannot destroy itself.	157	# cannot destroy itself.
162	my @destroy;	158	our @destroy;
163	my $manager;	159	our $manager;
164		160
165	$manager = new Coro sub {	161	$manager = new Coro sub {
166	while () {	162	while () {
167	(shift @destroy)->_cancel	163	Coro::_cancel shift @destroy
168	while @destroy;	164	while @destroy;
169		165
170	&schedule;	166	&schedule;
171	}	167	}
172	};	168	};
173	$manager->desc ("[coro manager]");	169	$manager->{desc} = "[coro manager]";
174	$manager->prio (PRIO_MAX);	170	$manager->prio (PRIO_MAX);
175		171
176	# static methods. not really.
177
178	=back	172	=back
179		173
180	=head2 STATIC METHODS	174	=head1 SIMPLE COROUTINE CREATION
181
182	Static methods are actually functions that operate on the current coroutine only.
183		175
184	=over 4	176	=over 4
185		177
186	=item async { ... } [@args...]	178	=item async { ... } [@args...]
187		179
188	Create a new asynchronous coroutine and return it's coroutine object	180	Create a new coroutine and return its coroutine object (usually
189	(usually unused). When the sub returns the new coroutine is automatically	181	unused). The coroutine will be put into the ready queue, so
		182	it will start running automatically on the next scheduler run.
		183
		184	The first argument is a codeblock/closure that should be executed in the
		185	coroutine. When it returns argument returns the coroutine is automatically
190	terminated.	186	terminated.
		187
		188	The remaining arguments are passed as arguments to the closure.
		189
		190	See the C<Coro::State::new> constructor for info about the coroutine
		191	environment in which coroutines are executed.
191		192
192	Calling C<exit> in a coroutine will do the same as calling exit outside	193	Calling C<exit> in a coroutine will do the same as calling exit outside
193	the coroutine. Likewise, when the coroutine dies, the program will exit,	194	the coroutine. Likewise, when the coroutine dies, the program will exit,
194	just as it would in the main program.	195	just as it would in the main program.
195		196
		197	If you do not want that, you can provide a default C<die> handler, or
		198	simply avoid dieing (by use of C<eval>).
		199
196	# create a new coroutine that just prints its arguments	200	Example: Create a new coroutine that just prints its arguments.
		201
197	async {	202	async {
198	print "@_\n";	203	print "@_\n";
199	} 1,2,3,4;	204	} 1,2,3,4;
200		205
201	=cut	206	=cut
207	}	212	}
208		213
209	=item async_pool { ... } [@args...]	214	=item async_pool { ... } [@args...]
210		215
211	Similar to C<async>, but uses a coroutine pool, so you should not call	216	Similar to C<async>, but uses a coroutine pool, so you should not call
212	terminate or join (although you are allowed to), and you get a coroutine	217	terminate or join on it (although you are allowed to), and you get a
213	that might have executed other code already (which can be good or bad :).	218	coroutine that might have executed other code already (which can be good
		219	or bad :).
214		220
		221	On the plus side, this function is about twice as fast as creating (and
		222	destroying) a completely new coroutine, so if you need a lot of generic
		223	coroutines in quick successsion, use C<async_pool>, not C<async>.
		224
215	Also, the block is executed in an C<eval> context and a warning will be	225	The code block is executed in an C<eval> context and a warning will be
216	issued in case of an exception instead of terminating the program, as	226	issued in case of an exception instead of terminating the program, as
217	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>	227	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
218	will not work in the expected way, unless you call terminate or cancel,	228	will not work in the expected way, unless you call terminate or cancel,
219	which somehow defeats the purpose of pooling.	229	which somehow defeats the purpose of pooling (but is fine in the
		230	exceptional case).
220		231
221	The priority will be reset to C<0> after each job, otherwise the coroutine	232	The priority will be reset to C<0> after each run, tracing will be
222	will be re-used "as-is".	233	disabled, the description will be reset and the default output filehandle
		234	gets restored, so you can change all these. Otherwise the coroutine will
		235	be re-used "as-is": most notably if you change other per-coroutine global
		236	stuff such as C<$/> you I<must needs> revert that change, which is most
		237	simply done by using local as in: C<< local $/ >>.
223		238
224	The pool size is limited to 8 idle coroutines (this can be adjusted by	239	The idle pool size is limited to C<8> idle coroutines (this can be
225	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as	240	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
226	required.	241	coros as required.
227		242
228	If you are concerned about pooled coroutines growing a lot because a	243	If you are concerned about pooled coroutines growing a lot because a
229	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {	244	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
230	terminate }> once per second or so to slowly replenish the pool.	245	{ terminate }> once per second or so to slowly replenish the pool. In
		246	addition to that, when the stacks used by a handler grows larger than 32kb
		247	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
231		248
232	=cut	249	=cut
233		250
234	our $POOL_SIZE = 8;	251	our $POOL_SIZE = 8;
235	our $MAX_POOL_RSS = 64 * 1024;	252	our $POOL_RSS = 32 * 1024;
236	our @pool;	253	our @async_pool;
237		254
238	sub pool_handler {	255	sub pool_handler {
239	while () {	256	while () {
240	$current->{desc} = "[async_pool]";
241
242	eval {	257	eval {
243	my ($cb, @arg) = @{ delete $current->{_invoke} or return };	258	&{&_pool_handler} while 1;
244	$cb->(@arg);
245	};	259	};
		260
246	warn $@ if $@;	261	warn $@ if $@;
247
248	last if @pool >= $POOL_SIZE \|\| $current->rss >= $MAX_POOL_RSS;
249
250	push @pool, $current;
251	$current->{desc} = "[async_pool idle]";
252	$current->save (Coro::State::SAVE_DEF);
253	$current->prio (0);
254	schedule;
255	}	262	}
256	}	263	}
257		264
258	sub async_pool(&@) {	265	=back
259	# this is also inlined into the unlock_scheduler
260	my $coro = (pop @pool) \|\| new Coro \&pool_handler;;
261		266
262	$coro->{_invoke} = [@_];	267	=head1 STATIC METHODS
263	$coro->ready;
264		268
265	$coro	269	Static methods are actually functions that implicitly operate on the
266	}	270	current coroutine.
		271
		272	=over 4
267		273
268	=item schedule	274	=item schedule
269		275
270	Calls the scheduler. Please note that the current coroutine will not be put	276	Calls the scheduler. The scheduler will find the next coroutine that is
		277	to be run from the ready queue and switches to it. The next coroutine
		278	to be run is simply the one with the highest priority that is longest
		279	in its ready queue. If there is no coroutine ready, it will clal the
		280	C<$Coro::idle> hook.
		281
		282	Please note that the current coroutine will I<not> be put into the ready
271	into the ready queue, so calling this function usually means you will	283	queue, so calling this function usually means you will never be called
272	never be called again unless something else (e.g. an event handler) calls	284	again unless something else (e.g. an event handler) calls C<< ->ready >>,
273	ready.	285	thus waking you up.
274		286
275	The canonical way to wait on external events is this:	287	This makes C<schedule> I<the> generic method to use to block the current
		288	coroutine and wait for events: first you remember the current coroutine in
		289	a variable, then arrange for some callback of yours to call C<< ->ready
		290	>> on that once some event happens, and last you call C<schedule> to put
		291	yourself to sleep. Note that a lot of things can wake your coroutine up,
		292	so you need to check whether the event indeed happened, e.g. by storing the
		293	status in a variable.
276		294
		295	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
		296
		297	=item cede
		298
		299	"Cede" to other coroutines. This function puts the current coroutine into
		300	the ready queue and calls C<schedule>, which has the effect of giving
		301	up the current "timeslice" to other coroutines of the same or higher
		302	priority. Once your coroutine gets its turn again it will automatically be
		303	resumed.
		304
		305	This function is often called C<yield> in other languages.
		306
		307	=item Coro::cede_notself
		308
		309	Works like cede, but is not exported by default and will cede to I<any>
		310	coroutine, regardless of priority. This is useful sometimes to ensure
		311	progress is made.
		312
		313	=item terminate [arg...]
		314
		315	Terminates the current coroutine with the given status values (see L<cancel>).
		316
		317	=item killall
		318
		319	Kills/terminates/cancels all coroutines except the currently running
		320	one. This is useful after a fork, either in the child or the parent, as
		321	usually only one of them should inherit the running coroutines.
		322
		323	Note that while this will try to free some of the main programs resources,
		324	you cannot free all of them, so if a coroutine that is not the main
		325	program calls this function, there will be some one-time resource leak.
		326
		327	=cut
		328
		329	sub killall {
		330	for (Coro::State::list) {
		331	$_->cancel
		332	if $_ != $current && UNIVERSAL::isa $_, "Coro";
277	{	333	}
278	# remember current coroutine	334	}
		335
		336	=back
		337
		338	=head1 COROUTINE OBJECT METHODS
		339
		340	These are the methods you can call on coroutine objects (or to create
		341	them).
		342
		343	=over 4
		344
		345	=item new Coro \&sub [, @args...]
		346
		347	Create a new coroutine and return it. When the sub returns, the coroutine
		348	automatically terminates as if C<terminate> with the returned values were
		349	called. To make the coroutine run you must first put it into the ready
		350	queue by calling the ready method.
		351
		352	See C<async> and C<Coro::State::new> for additional info about the
		353	coroutine environment.
		354
		355	=cut
		356
		357	sub _coro_run {
		358	terminate &{+shift};
		359	}
		360
		361	=item $success = $coroutine->ready
		362
		363	Put the given coroutine into the end of its ready queue (there is one
		364	queue for each priority) and return true. If the coroutine is already in
		365	the ready queue, do nothing and return false.
		366
		367	This ensures that the scheduler will resume this coroutine automatically
		368	once all the coroutines of higher priority and all coroutines of the same
		369	priority that were put into the ready queue earlier have been resumed.
		370
		371	=item $is_ready = $coroutine->is_ready
		372
		373	Return whether the coroutine is currently the ready queue or not,
		374
		375	=item $coroutine->cancel (arg...)
		376
		377	Terminates the given coroutine and makes it return the given arguments as
		378	status (default: the empty list). Never returns if the coroutine is the
		379	current coroutine.
		380
		381	=cut
		382
		383	sub cancel {
		384	my $self = shift;
		385
		386	if ($current == $self) {
		387	terminate @_;
		388	} else {
		389	$self->{_status} = [@_];
		390	$self->_cancel;
		391	}
		392	}
		393
		394	=item $coroutine->schedule_to
		395
		396	Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
		397	of continuing with the next coro from the ready queue, always switch to
		398	the given coroutine object (regardless of priority etc.). The readyness
		399	state of that coroutine isn't changed.
		400
		401	This is an advanced method for special cases - I'd love to hear about any
		402	uses for this one.
		403
		404	=item $coroutine->cede_to
		405
		406	Like C<schedule_to>, but puts the current coroutine into the ready
		407	queue. This has the effect of temporarily switching to the given
		408	coroutine, and continuing some time later.
		409
		410	This is an advanced method for special cases - I'd love to hear about any
		411	uses for this one.
		412
		413	=item $coroutine->throw ([$scalar])
		414
		415	If C<$throw> is specified and defined, it will be thrown as an exception
		416	inside the coroutine at the next convenient point in time. Otherwise
		417	clears the exception object.
		418
		419	Coro will check for the exception each time a schedule-like-function
		420	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		421	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		422	detect this case and return early in case an exception is pending.
		423
		424	The exception object will be thrown "as is" with the specified scalar in
		425	C<$@>, i.e. if it is a string, no line number or newline will be appended
		426	(unlike with C<die>).
		427
		428	This can be used as a softer means than C<cancel> to ask a coroutine to
		429	end itself, although there is no guarantee that the exception will lead to
		430	termination, and if the exception isn't caught it might well end the whole
		431	program.
		432
		433	You might also think of C<throw> as being the moral equivalent of
		434	C<kill>ing a coroutine with a signal (in this case, a scalar).
		435
		436	=item $coroutine->join
		437
		438	Wait until the coroutine terminates and return any values given to the
		439	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		440	from multiple coroutines, and all will be resumed and given the status
		441	return once the C<$coroutine> terminates.
		442
		443	=cut
		444
		445	sub join {
		446	my $self = shift;
		447
		448	unless ($self->{_status}) {
279	my $current = $Coro::current;	449	my $current = $current;
280		450
281	# register a hypothetical event handler	451	push @{$self->{_on_destroy}}, sub {
282	on_event_invoke sub {
283	# wake up sleeping coroutine
284	$current->ready;	452	$current->ready;
285	undef $current;	453	undef $current;
286	};	454	};
287		455
288	# call schedule until event occurred.
289	# in case we are woken up for other reasons
290	# (current still defined), loop.
291	Coro::schedule while $current;
292	}
293
294	=item cede
295
296	"Cede" to other coroutines. This function puts the current coroutine into the
297	ready queue and calls C<schedule>, which has the effect of giving up the
298	current "timeslice" to other coroutines of the same or higher priority.
299
300	Returns true if at least one coroutine switch has happened.
301
302	=item Coro::cede_notself
303
304	Works like cede, but is not exported by default and will cede to any
305	coroutine, regardless of priority, once.
306
307	Returns true if at least one coroutine switch has happened.
308
309	=item terminate [arg...]
310
311	Terminates the current coroutine with the given status values (see L<cancel>).
312
313	=cut
314
315	sub terminate {
316	$current->cancel (@_);
317	}
318
319	=back
320
321	# dynamic methods
322
323	=head2 COROUTINE METHODS
324
325	These are the methods you can call on coroutine objects.
326
327	=over 4
328
329	=item new Coro \&sub [, @args...]
330
331	Create a new coroutine and return it. When the sub returns the coroutine
332	automatically terminates as if C<terminate> with the returned values were
333	called. To make the coroutine run you must first put it into the ready queue
334	by calling the ready method.
335
336	See C<async> for additional discussion.
337
338	=cut
339
340	sub _run_coro {
341	terminate &{+shift};
342	}
343
344	sub new {
345	my $class = shift;
346
347	$class->SUPER::new (\&_run_coro, @_)
348	}
349
350	=item $success = $coroutine->ready
351
352	Put the given coroutine into the ready queue (according to it's priority)
353	and return true. If the coroutine is already in the ready queue, do nothing
354	and return false.
355
356	=item $is_ready = $coroutine->is_ready
357
358	Return wether the coroutine is currently the ready queue or not,
359
360	=item $coroutine->cancel (arg...)
361
362	Terminates the given coroutine and makes it return the given arguments as
363	status (default: the empty list). Never returns if the coroutine is the
364	current coroutine.
365
366	=cut
367
368	sub cancel {
369	my $self = shift;
370	$self->{status} = [@_];
371
372	if ($current == $self) {
373	push @destroy, $self;
374	$manager->ready;
375	&schedule while 1;
376	} else {
377	$self->_cancel;
378	}
379	}
380
381	=item $coroutine->join
382
383	Wait until the coroutine terminates and return any values given to the
384	C<terminate> or C<cancel> functions. C<join> can be called multiple times
385	from multiple coroutine.
386
387	=cut
388
389	sub join {
390	my $self = shift;
391
392	unless ($self->{status}) {
393	my $current = $current;
394
395	push @{$self->{destroy_cb}}, sub {
396	$current->ready;
397	undef $current;
398	};
399
400	&schedule while $current;	456	&schedule while $current;
401	}	457	}
402		458
403	wantarray ? @{$self->{status}} : $self->{status}[0];	459	wantarray ? @{$self->{_status}} : $self->{_status}[0];
404	}	460	}
405		461
406	=item $coroutine->on_destroy (\&cb)	462	=item $coroutine->on_destroy (\&cb)
407		463
408	Registers a callback that is called when this coroutine gets destroyed,	464	Registers a callback that is called when this coroutine gets destroyed,
409	but before it is joined. The callback gets passed the terminate arguments,	465	but before it is joined. The callback gets passed the terminate arguments,
410	if any.	466	if any, and I<must not> die, under any circumstances.
411		467
412	=cut	468	=cut
413		469
414	sub on_destroy {	470	sub on_destroy {
415	my ($self, $cb) = @_;	471	my ($self, $cb) = @_;
416		472
417	push @{ $self->{destroy_cb} }, $cb;	473	push @{ $self->{_on_destroy} }, $cb;
418	}	474	}
419		475
420	=item $oldprio = $coroutine->prio ($newprio)	476	=item $oldprio = $coroutine->prio ($newprio)
421		477
422	Sets (or gets, if the argument is missing) the priority of the	478	Sets (or gets, if the argument is missing) the priority of the
…		…
445	higher values mean lower priority, just as in unix).	501	higher values mean lower priority, just as in unix).
446		502
447	=item $olddesc = $coroutine->desc ($newdesc)	503	=item $olddesc = $coroutine->desc ($newdesc)
448		504
449	Sets (or gets in case the argument is missing) the description for this	505	Sets (or gets in case the argument is missing) the description for this
450	coroutine. This is just a free-form string you can associate with a coroutine.	506	coroutine. This is just a free-form string you can associate with a
		507	coroutine.
		508
		509	This method simply sets the C<< $coroutine->{desc} >> member to the given
		510	string. You can modify this member directly if you wish.
451		511
452	=cut	512	=cut
453		513
454	sub desc {	514	sub desc {
455	my $old = $_[0]{desc};	515	my $old = $_[0]{desc};
456	$_[0]{desc} = $_[1] if @_ > 1;	516	$_[0]{desc} = $_[1] if @_ > 1;
457	$old;	517	$old;
458	}	518	}
459		519
		520	sub transfer {
		521	require Carp;
		522	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		523	}
		524
460	=back	525	=back
461		526
462	=head2 GLOBAL FUNCTIONS	527	=head1 GLOBAL FUNCTIONS
463		528
464	=over 4	529	=over 4
465		530
466	=item Coro::nready	531	=item Coro::nready
467		532
468	Returns the number of coroutines that are currently in the ready state,	533	Returns the number of coroutines that are currently in the ready state,
469	i.e. that can be switched to. The value C<0> means that the only runnable	534	i.e. that can be switched to by calling C<schedule> directory or
		535	indirectly. The value C<0> means that the only runnable coroutine is the
470	coroutine is the currently running one, so C<cede> would have no effect,	536	currently running one, so C<cede> would have no effect, and C<schedule>
471	and C<schedule> would cause a deadlock unless there is an idle handler	537	would cause a deadlock unless there is an idle handler that wakes up some
472	that wakes up some coroutines.	538	coroutines.
473		539
474	=item my $guard = Coro::guard { ... }	540	=item my $guard = Coro::guard { ... }
475		541
476	This creates and returns a guard object. Nothing happens until the object	542	This function still exists, but is deprecated. Please use the
477	gets destroyed, in which case the codeblock given as argument will be	543	C<Guard::guard> function instead.
478	executed. This is useful to free locks or other resources in case of a
479	runtime error or when the coroutine gets canceled, as in both cases the
480	guard block will be executed. The guard object supports only one method,
481	C<< ->cancel >>, which will keep the codeblock from being executed.
482		544
483	Example: set some flag and clear it again when the coroutine gets canceled
484	or the function returns:
485
486	sub do_something {
487	my $guard = Coro::guard { $busy = 0 };
488	$busy = 1;
489
490	# do something that requires $busy to be true
491	}
492
493	=cut	545	=cut
494		546
495	sub guard(&) {	547	BEGIN { *guard = \&Guard::guard }
496	bless \(my $cb = $_[0]), "Coro::guard"
497	}
498
499	sub Coro::guard::cancel {
500	${$_[0]} = sub { };
501	}
502
503	sub Coro::guard::DESTROY {
504	${$_[0]}->();
505	}
506
507		548
508	=item unblock_sub { ... }	549	=item unblock_sub { ... }
509		550
510	This utility function takes a BLOCK or code reference and "unblocks" it,	551	This utility function takes a BLOCK or code reference and "unblocks" it,
511	returning the new coderef. This means that the new coderef will return	552	returning a new coderef. Unblocking means that calling the new coderef
512	immediately without blocking, returning nothing, while the original code	553	will return immediately without blocking, returning nothing, while the
513	ref will be called (with parameters) from within its own coroutine.	554	original code ref will be called (with parameters) from within another
		555	coroutine.
514		556
515	The reason this function exists is that many event libraries (such as the	557	The reason this function exists is that many event libraries (such as the
516	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	558	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
517	of thread-safety). This means you must not block within event callbacks,	559	of reentrancy). This means you must not block within event callbacks,
518	otherwise you might suffer from crashes or worse.	560	otherwise you might suffer from crashes or worse. The only event library
		561	currently known that is safe to use without C<unblock_sub> is L<EV>.
519		562
520	This function allows your callbacks to block by executing them in another	563	This function allows your callbacks to block by executing them in another
521	coroutine where it is safe to block. One example where blocking is handy	564	coroutine where it is safe to block. One example where blocking is handy
522	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	565	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
523	disk.	566	disk, for example.
524		567
525	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	568	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
526	creating event callbacks that want to block.	569	creating event callbacks that want to block.
		570
		571	If your handler does not plan to block (e.g. simply sends a message to
		572	another coroutine, or puts some other coroutine into the ready queue),
		573	there is no reason to use C<unblock_sub>.
		574
		575	Note that you also need to use C<unblock_sub> for any other callbacks that
		576	are indirectly executed by any C-based event loop. For example, when you
		577	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		578	provides callbacks that are the result of some event callback, then you
		579	must not block either, or use C<unblock_sub>.
527		580
528	=cut	581	=cut
529		582
530	our @unblock_queue;	583	our @unblock_queue;
531		584
…		…
534	# return immediately and can be reused) and because we cannot cede	587	# return immediately and can be reused) and because we cannot cede
535	# inside an event callback.	588	# inside an event callback.
536	our $unblock_scheduler = new Coro sub {	589	our $unblock_scheduler = new Coro sub {
537	while () {	590	while () {
538	while (my $cb = pop @unblock_queue) {	591	while (my $cb = pop @unblock_queue) {
539	# this is an inlined copy of async_pool	592	&async_pool (@$cb);
540	my $coro = (pop @pool or new Coro \&pool_handler);
541		593
542	$coro->{_invoke} = $cb;
543	$coro->ready;
544	cede; # for short-lived callbacks, this reduces pressure on the coro pool	594	# for short-lived callbacks, this reduces pressure on the coro pool
		595	# as the chance is very high that the async_poll coro will be back
		596	# in the idle state when cede returns
		597	cede;
545	}	598	}
546	schedule; # sleep well	599	schedule; # sleep well
547	}	600	}
548	};	601	};
549	$unblock_scheduler->desc ("[unblock_sub scheduler]");	602	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
550		603
551	sub unblock_sub(&) {	604	sub unblock_sub(&) {
552	my $cb = shift;	605	my $cb = shift;
553		606
554	sub {	607	sub {
555	unshift @unblock_queue, [$cb, @_];	608	unshift @unblock_queue, [$cb, @_];
556	$unblock_scheduler->ready;	609	$unblock_scheduler->ready;
557	}	610	}
558	}	611	}
559		612
		613	=item $cb = Coro::rouse_cb
		614
		615	Create and return a "rouse callback". That's a code reference that,
		616	when called, will remember a copy of its arguments and notify the owner
		617	coroutine of the callback.
		618
		619	See the next function.
		620
		621	=item @args = Coro::rouse_wait [$cb]
		622
		623	Wait for the specified rouse callback (or the last one that was created in
		624	this coroutine).
		625
		626	As soon as the callback is invoked (or when the callback was invoked
		627	before C<rouse_wait>), it will return the arguments originally passed to
		628	the rouse callback.
		629
		630	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		631
560	=back	632	=back
561		633
562	=cut	634	=cut
563		635
564	1;	636	1;
565		637
		638	=head1 HOW TO WAIT FOR A CALLBACK
		639
		640	It is very common for a coroutine to wait for some callback to be
		641	called. This occurs naturally when you use coroutines in an otherwise
		642	event-based program, or when you use event-based libraries.
		643
		644	These typically register a callback for some event, and call that callback
		645	when the event occured. In a coroutine, however, you typically want to
		646	just wait for the event, simplyifying things.
		647
		648	For example C<< AnyEvent->child >> registers a callback to be called when
		649	a specific child has exited:
		650
		651	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		652
		653	But from withina coroutine, you often just want to write this:
		654
		655	my $status = wait_for_child $pid;
		656
		657	Coro offers two functions specifically designed to make this easy,
		658	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		659
		660	The first function, C<rouse_cb>, generates and returns a callback that,
		661	when invoked, will save its arguments and notify the coroutine that
		662	created the callback.
		663
		664	The second function, C<rouse_wait>, waits for the callback to be called
		665	(by calling C<schedule> to go to sleep) and returns the arguments
		666	originally passed to the callback.
		667
		668	Using these functions, it becomes easy to write the C<wait_for_child>
		669	function mentioned above:
		670
		671	sub wait_for_child($) {
		672	my ($pid) = @_;
		673
		674	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		675
		676	my ($rpid, $rstatus) = Coro::rouse_wait;
		677	$rstatus
		678	}
		679
		680	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		681	you can roll your own, using C<schedule>:
		682
		683	sub wait_for_child($) {
		684	my ($pid) = @_;
		685
		686	# store the current coroutine in $current,
		687	# and provide result variables for the closure passed to ->child
		688	my $current = $Coro::current;
		689	my ($done, $rstatus);
		690
		691	# pass a closure to ->child
		692	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		693	$rstatus = $_[1]; # remember rstatus
		694	$done = 1; # mark $rstatus as valud
		695	});
		696
		697	# wait until the closure has been called
		698	schedule while !$done;
		699
		700	$rstatus
		701	}
		702
		703
566	=head1 BUGS/LIMITATIONS	704	=head1 BUGS/LIMITATIONS
567		705
568	- you must make very sure that no coro is still active on global	706	=over 4
569	destruction. very bad things might happen otherwise (usually segfaults).
570		707
		708	=item fork with pthread backend
		709
		710	When Coro is compiled using the pthread backend (which isn't recommended
		711	but required on many BSDs as their libcs are completely broken), then
		712	coroutines will not survive a fork. There is no known workaround except to
		713	fix your libc and use a saner backend.
		714
		715	=item perl process emulation ("threads")
		716
571	- this module is not thread-safe. You should only ever use this module	717	This module is not perl-pseudo-thread-safe. You should only ever use this
572	from the same thread (this requirement might be loosened in the future	718	module from the first thread (this requirement might be removed in the
573	to allow per-thread schedulers, but Coro::State does not yet allow	719	future to allow per-thread schedulers, but Coro::State does not yet allow
574	this).	720	this). I recommend disabling thread support and using processes, as having
		721	the windows process emulation enabled under unix roughly halves perl
		722	performance, even when not used.
		723
		724	=item coroutine switching not signal safe
		725
		726	You must not switch to another coroutine from within a signal handler
		727	(only relevant with %SIG - most event libraries provide safe signals).
		728
		729	That means you I<MUST NOT> call any function that might "block" the
		730	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		731	anything that calls those. Everything else, including calling C<ready>,
		732	works.
		733
		734	=back
		735
575		736
576	=head1 SEE ALSO	737	=head1 SEE ALSO
577		738
		739	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		740
		741	Debugging: L<Coro::Debug>.
		742
578	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	743	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
579		744
580	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	745	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		746	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
581		747
582	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	748	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
583		749
584	Embedding: L<Coro:MakeMaker>	750	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		751	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		752	L<Coro::Select>.
		753
		754	XS API: L<Coro::MakeMaker>.
		755
		756	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
585		757
586	=head1 AUTHOR	758	=head1 AUTHOR
587		759
588	Marc Lehmann <schmorp@schmorp.de>	760	Marc Lehmann <schmorp@schmorp.de>
589	http://home.schmorp.de/	761	http://home.schmorp.de/

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Revision 1.244 by root, Sat Dec 13 22:08:13 2008 UTC