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

Comparing Coro/Coro.pm (file contents):
Revision 1.92 by root, Fri Dec 1 03:47:55 2006 UTC vs.
Revision 1.195 by root, Wed Jul 23 22:15:25 2008 UTC

…		…
2		2
3	Coro - coroutine process abstraction	3	Coro - coroutine process abstraction
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	my $lock = new Coro::Semaphore;
19	cede;	22	my $locked;
		23
		24	$lock->down;
		25	$locked = 1;
		26	$lock->up;
20		27
21	=head1 DESCRIPTION	28	=head1 DESCRIPTION
22		29
23	This module collection manages coroutines. Coroutines are similar to	30	This module collection manages coroutines. Coroutines are similar to
24	threads but don't run in parallel.	31	threads but don't (in general) run in parallel at the same time even
		32	on SMP machines. The specific flavor of coroutine used in this module
		33	also guarantees you that it will not switch between coroutines unless
		34	necessary, at easily-identified points in your program, so locking and
		35	parallel access are rarely an issue, making coroutine programming much
		36	safer and easier than threads programming.
25		37
		38	Unlike a normal perl program, however, coroutines allow you to have
		39	multiple running interpreters that share data, which is especially useful
		40	to code pseudo-parallel processes and for event-based programming, such as
		41	multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to
		42	learn more.
		43
		44	Coroutines are also useful because Perl has no support for threads (the so
		45	called "threads" that perl offers are nothing more than the (bad) process
		46	emulation coming from the Windows platform: On standard operating systems
		47	they serve no purpose whatsoever, except by making your programs slow and
		48	making them use a lot of memory. Best disable them when building perl, or
		49	aks your software vendor/distributor to do it for you).
		50
26	In this module, coroutines are defined as "callchain + lexical variables	51	In this module, coroutines are defined as "callchain + lexical variables +
27	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own	52	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
28	callchain, it's own set of lexicals and it's own set of perl's most	53	its own set of lexicals and its own set of perls most important global
29	important global variables.	54	variables (see L<Coro::State> for more configuration).
30		55
31	=cut	56	=cut
32		57
33	package Coro;	58	package Coro;
34		59
…		…
41		66
42	our $idle; # idle handler	67	our $idle; # idle handler
43	our $main; # main coroutine	68	our $main; # main coroutine
44	our $current; # current coroutine	69	our $current; # current coroutine
45		70
46	our $VERSION = '3.0';	71	our $VERSION = 4.745;
47		72
48	our @EXPORT = qw(async cede schedule terminate current unblock_sub);	73	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
49	our %EXPORT_TAGS = (	74	our %EXPORT_TAGS = (
50	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	75	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51	);	76	);
52	our @EXPORT_OK = @{$EXPORT_TAGS{prio}};	77	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
53
54	{
55	my @async;
56	my $init;
57
58	# this way of handling attributes simply is NOT scalable ;()
59	sub import {
60	no strict 'refs';
61
62	Coro->export_to_level(1, @_);
63
64	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
65	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
66	my ($package, $ref) = (shift, shift);
67	my @attrs;
68	for (@_) {
69	if ($_ eq "Coro") {
70	push @async, $ref;
71	unless ($init++) {
72	eval q{
73	sub INIT {
74	&async(pop @async) while @async;
75	}
76	};
77	}
78	} else {
79	push @attrs, $_;
80	}
81	}
82	return $old ? $old->($package, $ref, @attrs) : @attrs;
83	};
84	}
85
86	}
87		78
88	=over 4	79	=over 4
89		80
90	=item $main	81	=item $Coro::main
91		82
92	This coroutine represents the main program.	83	This variable stores the coroutine object that represents the main
		84	program. While you cna C<ready> it and do most other things you can do to
		85	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		86	wether you are running in the main program or not.
93		87
94	=cut	88	=cut
95		89
96	$main = new Coro;	90	$main = new Coro;
97		91
98	=item $current (or as function: current)	92	=item $Coro::current
99		93
100	The current coroutine (the last coroutine switched to). The initial value	94	The coroutine object representing the current coroutine (the last
		95	coroutine that the Coro scheduler switched to). The initial value is
101	is C<$main> (of course).	96	C<$main> (of course).
102		97
103	This variable is B<strictly> I<read-only>. It is provided for performance	98	This variable is B<strictly> I<read-only>. You can take copies of the
104	reasons. If performance is not essentiel you are encouraged to use the	99	value stored in it and use it as any other coroutine object, but you must
105	C<Coro::current> function instead.	100	not otherwise modify the variable itself.
106		101
107	=cut	102	=cut
		103
		104	$main->{desc} = "[main::]";
108		105
109	# maybe some other module used Coro::Specific before...	106	# maybe some other module used Coro::Specific before...
110	if ($current) {
111	$main->{specific} = $current->{specific};	107	$main->{_specific} = $current->{_specific}
112	}	108	if $current;
113		109
114	$current = $main;	110	_set_current $main;
115		111
116	sub current() { $current }	112	sub current() { $current } # [DEPRECATED]
117		113
118	=item $idle	114	=item $Coro::idle
119		115
120	A callback that is called whenever the scheduler finds no ready coroutines	116	This variable is mainly useful to integrate Coro into event loops. It is
121	to run. The default implementation prints "FATAL: deadlock detected" and	117	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
122	exits, because the program has no other way to continue.	118	pretty low-level functionality.
		119
		120	This variable stores a callback that is called whenever the scheduler
		121	finds no ready coroutines to run. The default implementation prints
		122	"FATAL: deadlock detected" and exits, because the program has no other way
		123	to continue.
123		124
124	This hook is overwritten by modules such as C<Coro::Timer> and	125	This hook is overwritten by modules such as C<Coro::Timer> and
125	C<Coro::Event> to wait on an external event that hopefully wake up a	126	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
126	coroutine so the scheduler can run it.	127	coroutine so the scheduler can run it.
127		128
		129	Note that the callback I<must not>, under any circumstances, block
		130	the current coroutine. Normally, this is achieved by having an "idle
		131	coroutine" that calls the event loop and then blocks again, and then
		132	readying that coroutine in the idle handler.
		133
		134	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		135	technique.
		136
128	Please note that if your callback recursively invokes perl (e.g. for event	137	Please note that if your callback recursively invokes perl (e.g. for event
129	handlers), then it must be prepared to be called recursively.	138	handlers), then it must be prepared to be called recursively itself.
130		139
131	=cut	140	=cut
132		141
133	$idle = sub {	142	$idle = sub {
134	print STDERR "FATAL: deadlock detected\n";	143	require Carp;
135	exit (51);	144	Carp::croak ("FATAL: deadlock detected");
136	};	145	};
		146
		147	sub _cancel {
		148	my ($self) = @_;
		149
		150	# free coroutine data and mark as destructed
		151	$self->_destroy
		152	or return;
		153
		154	# call all destruction callbacks
		155	$_->(@{$self->{_status}})
		156	for @{(delete $self->{_on_destroy}) \|\| []};
		157	}
137		158
138	# this coroutine is necessary because a coroutine	159	# this coroutine is necessary because a coroutine
139	# cannot destroy itself.	160	# cannot destroy itself.
140	my @destroy;	161	my @destroy;
		162	my $manager;
		163
141	my $manager; $manager = new Coro sub {	164	$manager = new Coro sub {
142	while () {	165	while () {
143	# by overwriting the state object with the manager we destroy it	166	(shift @destroy)->_cancel
144	# while still being able to schedule this coroutine (in case it has
145	# been readied multiple times. this is harmless since the manager
146	# can be called as many times as neccessary and will always
147	# remove itself from the runqueue
148	while (@destroy) {	167	while @destroy;
149	my $coro = pop @destroy;
150	$coro->{status} \|\|= [];
151	$_->ready for @{delete $coro->{join} \|\| []};
152		168
153	# the next line destroys the coro state, but keeps the
154	# coroutine itself intact (we basically make it a zombie
155	# coroutine that always runs the manager thread, so it's possible
156	# to transfer() to this coroutine).
157	$coro->_clone_state_from ($manager);
158	}
159	&schedule;	169	&schedule;
160	}	170	}
161	};	171	};
162		172	$manager->desc ("[coro manager]");
163	# static methods. not really.	173	$manager->prio (PRIO_MAX);
164		174
165	=back	175	=back
166		176
167	=head2 STATIC METHODS	177	=head2 SIMPLE COROUTINE CREATION
168
169	Static methods are actually functions that operate on the current coroutine only.
170		178
171	=over 4	179	=over 4
172		180
173	=item async { ... } [@args...]	181	=item async { ... } [@args...]
174		182
175	Create a new asynchronous coroutine and return it's coroutine object	183	Create a new coroutine and return it's coroutine object (usually
176	(usually unused). When the sub returns the new coroutine is automatically	184	unused). The coroutine 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	coroutine. When it returns argument returns the coroutine is automatically
177	terminated.	189	terminated.
178		190
179	Calling C<exit> in a coroutine will not work correctly, so do not do that.	191	The remaining arguments are passed as arguments to the closure.
180		192
181	When the coroutine dies, the program will exit, just as in the main	193	See the C<Coro::State::new> constructor for info about the coroutine
182	program.	194	environment in which coroutines are executed.
183		195
		196	Calling C<exit> in a coroutine will do the same as calling exit outside
		197	the coroutine. Likewise, when the coroutine 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
184	# create a new coroutine that just prints its arguments	203	Example: Create a new coroutine that just prints its arguments.
		204
185	async {	205	async {
186	print "@_\n";	206	print "@_\n";
187	} 1,2,3,4;	207	} 1,2,3,4;
188		208
189	=cut	209	=cut
190		210
191	sub async(&@) {	211	sub async(&@) {
192	my $pid = new Coro @_;	212	my $coro = new Coro @_;
193	$pid->ready;	213	$coro->ready;
194	$pid	214	$coro
195	}	215	}
		216
		217	=item async_pool { ... } [@args...]
		218
		219	Similar to C<async>, but uses a coroutine pool, so you should not call
		220	terminate or join on it (although you are allowed to), and you get a
		221	coroutine that might have executed other code already (which can be good
		222	or bad :).
		223
		224	On the plus side, this function is faster than creating (and destroying)
		225	a completely new coroutine, so if you need a lot of generic coroutines in
		226	quick successsion, use C<async_pool>, not C<async>.
		227
		228	The code block is executed in an C<eval> context and a warning will be
		229	issued in case of an exception instead of terminating the program, as
		230	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		231	will not work in the expected way, unless you call terminate or cancel,
		232	which somehow defeats the purpose of pooling (but is fine in the
		233	exceptional case).
		234
		235	The priority will be reset to C<0> after each run, tracing will be
		236	disabled, the description will be reset and the default output filehandle
		237	gets restored, so you can change all these. Otherwise the coroutine will
		238	be re-used "as-is": most notably if you change other per-coroutine global
		239	stuff such as C<$/> you I<must needs> to revert that change, which is most
		240	simply done by using local as in: C< local $/ >.
		241
		242	The pool size is limited to C<8> idle coroutines (this can be adjusted by
		243	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		244	required.
		245
		246	If you are concerned about pooled coroutines 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 16kb
		250	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		251
		252	=cut
		253
		254	our $POOL_SIZE = 8;
		255	our $POOL_RSS = 16 * 1024;
		256	our @async_pool;
		257
		258	sub pool_handler {
		259	my $cb;
		260
		261	while () {
		262	eval {
		263	while () {
		264	_pool_1 $cb;
		265	&$cb;
		266	_pool_2 $cb;
		267	&schedule;
		268	}
		269	};
		270
		271	if ($@) {
		272	last if $@ eq "\3async_pool terminate\2\n";
		273	warn $@;
		274	}
		275	}
		276	}
		277
		278	sub async_pool(&@) {
		279	# this is also inlined into the unlock_scheduler
		280	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		281
		282	$coro->{_invoke} = [@_];
		283	$coro->ready;
		284
		285	$coro
		286	}
		287
		288	=back
		289
		290	=head2 STATIC METHODS
		291
		292	Static methods are actually functions that operate on the current coroutine.
		293
		294	=over 4
196		295
197	=item schedule	296	=item schedule
198		297
199	Calls the scheduler. Please note that the current coroutine will not be put	298	Calls the scheduler. The scheduler will find the next coroutine that is
		299	to be run from the ready queue and switches to it. The next coroutine
		300	to be run is simply the one with the highest priority that is longest
		301	in its ready queue. If there is no coroutine ready, it will clal the
		302	C<$Coro::idle> hook.
		303
		304	Please note that the current coroutine will I<not> be put into the ready
200	into the ready queue, so calling this function usually means you will	305	queue, so calling this function usually means you will never be called
201	never be called again unless something else (e.g. an event handler) calls	306	again unless something else (e.g. an event handler) calls C<< ->ready >>,
202	ready.	307	thus waking you up.
		308
		309	This makes C<schedule> I<the> generic method to use to block the current
		310	coroutine and wait for events: first you remember the current coroutine in
		311	a variable, then arrange for some callback of yours to call C<< ->ready
		312	>> on that once some event happens, and last you call C<schedule> to put
		313	yourself to sleep. Note that a lot of things can wake your coroutine up,
		314	so you need to check wether the event indeed happened, e.g. by storing the
		315	status in a variable.
203		316
204	The canonical way to wait on external events is this:	317	The canonical way to wait on external events is this:
205		318
206	{	319	{
207	# remember current coroutine	320	# remember current coroutine
…		…
212	# wake up sleeping coroutine	325	# wake up sleeping coroutine
213	$current->ready;	326	$current->ready;
214	undef $current;	327	undef $current;
215	};	328	};
216		329
217	# call schedule until event occured.	330	# call schedule until event occurred.
218	# in case we are woken up for other reasons	331	# in case we are woken up for other reasons
219	# (current still defined), loop.	332	# (current still defined), loop.
220	Coro::schedule while $current;	333	Coro::schedule while $current;
221	}	334	}
222		335
223	=item cede	336	=item cede
224		337
225	"Cede" to other coroutines. This function puts the current coroutine into the	338	"Cede" to other coroutines. This function puts the current coroutine into
226	ready queue and calls C<schedule>, which has the effect of giving up the	339	the ready queue and calls C<schedule>, which has the effect of giving
227	current "timeslice" to other coroutines of the same or higher priority.	340	up the current "timeslice" to other coroutines of the same or higher
		341	priority. Once your coroutine gets its turn again it will automatically be
		342	resumed.
		343
		344	This function is often called C<yield> in other languages.
		345
		346	=item Coro::cede_notself
		347
		348	Works like cede, but is not exported by default and will cede to I<any>
		349	coroutine, regardless of priority. This is useful sometimes to ensure
		350	progress is made.
228		351
229	=item terminate [arg...]	352	=item terminate [arg...]
230		353
231	Terminates the current coroutine with the given status values (see L<cancel>).	354	Terminates the current coroutine with the given status values (see L<cancel>).
		355
		356	=item killall
		357
		358	Kills/terminates/cancels all coroutines except the currently running
		359	one. This is useful after a fork, either in the child or the parent, as
		360	usually only one of them should inherit the running coroutines.
		361
		362	Note that while this will try to free some of the main programs resources,
		363	you cnanot free all of them, so if a coroutine that is not the main
		364	program calls this function, there will be some one-time resource leak.
232		365
233	=cut	366	=cut
234		367
235	sub terminate {	368	sub terminate {
236	$current->cancel (@_);	369	$current->cancel (@_);
237	}	370	}
238		371
		372	sub killall {
		373	for (Coro::State::list) {
		374	$_->cancel
		375	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		376	}
		377	}
		378
239	=back	379	=back
240		380
241	# dynamic methods
242
243	=head2 COROUTINE METHODS	381	=head2 COROUTINE METHODS
244		382
245	These are the methods you can call on coroutine objects.	383	These are the methods you can call on coroutine objects (or to create
		384	them).
246		385
247	=over 4	386	=over 4
248		387
249	=item new Coro \&sub [, @args...]	388	=item new Coro \&sub [, @args...]
250		389
251	Create a new coroutine and return it. When the sub returns the coroutine	390	Create a new coroutine and return it. When the sub returns, the coroutine
252	automatically terminates as if C<terminate> with the returned values were	391	automatically terminates as if C<terminate> with the returned values were
253	called. To make the coroutine run you must first put it into the ready queue	392	called. To make the coroutine run you must first put it into the ready
254	by calling the ready method.	393	queue by calling the ready method.
255		394
256	Calling C<exit> in a coroutine will not work correctly, so do not do that.	395	See C<async> and C<Coro::State::new> for additional info about the
		396	coroutine environment.
257		397
258	=cut	398	=cut
259		399
260	sub _new_coro {	400	sub _run_coro {
261	terminate &{+shift};	401	terminate &{+shift};
262	}	402	}
263		403
264	sub new {	404	sub new {
265	my $class = shift;	405	my $class = shift;
266		406
267	$class->SUPER::new (\&_new_coro, @_)	407	$class->SUPER::new (\&_run_coro, @_)
268	}	408	}
269		409
270	=item $success = $coroutine->ready	410	=item $success = $coroutine->ready
271		411
272	Put the given coroutine into the ready queue (according to it's priority)	412	Put the given coroutine into the end of its ready queue (there is one
273	and return true. If the coroutine is already in the ready queue, do nothing	413	queue for each priority) and return true. If the coroutine is already in
274	and return false.	414	the ready queue, do nothing and return false.
		415
		416	This ensures that the scheduler will resume this coroutine automatically
		417	once all the coroutines of higher priority and all coroutines of the same
		418	priority that were put into the ready queue earlier have been resumed.
275		419
276	=item $is_ready = $coroutine->is_ready	420	=item $is_ready = $coroutine->is_ready
277		421
278	Return wether the coroutine is currently the ready queue or not,	422	Return wether the coroutine is currently the ready queue or not,
279		423
280	=item $coroutine->cancel (arg...)	424	=item $coroutine->cancel (arg...)
281		425
282	Terminates the given coroutine and makes it return the given arguments as	426	Terminates the given coroutine and makes it return the given arguments as
283	status (default: the empty list).	427	status (default: the empty list). Never returns if the coroutine is the
		428	current coroutine.
284		429
285	=cut	430	=cut
286		431
287	sub cancel {	432	sub cancel {
288	my $self = shift;	433	my $self = shift;
289	$self->{status} = [@_];	434	$self->{_status} = [@_];
		435
		436	if ($current == $self) {
290	push @destroy, $self;	437	push @destroy, $self;
291	$manager->ready;	438	$manager->ready;
292	&schedule if $current == $self;	439	&schedule while 1;
		440	} else {
		441	$self->_cancel;
		442	}
293	}	443	}
294		444
295	=item $coroutine->join	445	=item $coroutine->join
296		446
297	Wait until the coroutine terminates and return any values given to the	447	Wait until the coroutine terminates and return any values given to the
298	C<terminate> or C<cancel> functions. C<join> can be called multiple times	448	C<terminate> or C<cancel> functions. C<join> can be called concurrently
299	from multiple coroutine.	449	from multiple coroutines, and all will be resumed and given the status
		450	return once the C<$coroutine> terminates.
300		451
301	=cut	452	=cut
302		453
303	sub join {	454	sub join {
304	my $self = shift;	455	my $self = shift;
		456
305	unless ($self->{status}) {	457	unless ($self->{_status}) {
306	push @{$self->{join}}, $current;	458	my $current = $current;
307	&schedule;	459
		460	push @{$self->{_on_destroy}}, sub {
		461	$current->ready;
		462	undef $current;
		463	};
		464
		465	&schedule while $current;
308	}	466	}
		467
309	wantarray ? @{$self->{status}} : $self->{status}[0];	468	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		469	}
		470
		471	=item $coroutine->on_destroy (\&cb)
		472
		473	Registers a callback that is called when this coroutine gets destroyed,
		474	but before it is joined. The callback gets passed the terminate arguments,
		475	if any, and I<must not> die, under any circumstances.
		476
		477	=cut
		478
		479	sub on_destroy {
		480	my ($self, $cb) = @_;
		481
		482	push @{ $self->{_on_destroy} }, $cb;
310	}	483	}
311		484
312	=item $oldprio = $coroutine->prio ($newprio)	485	=item $oldprio = $coroutine->prio ($newprio)
313		486
314	Sets (or gets, if the argument is missing) the priority of the	487	Sets (or gets, if the argument is missing) the priority of the
…		…
339	=item $olddesc = $coroutine->desc ($newdesc)	512	=item $olddesc = $coroutine->desc ($newdesc)
340		513
341	Sets (or gets in case the argument is missing) the description for this	514	Sets (or gets in case the argument is missing) the description for this
342	coroutine. This is just a free-form string you can associate with a coroutine.	515	coroutine. This is just a free-form string you can associate with a coroutine.
343		516
		517	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
		518	can modify this member directly if you wish.
		519
		520	=item $coroutine->throw ([$scalar])
		521
		522	If C<$throw> is specified and defined, it will be thrown as an exception
		523	inside the coroutine at the next convinient point in time (usually after
		524	it gains control at the next schedule/transfer/cede). Otherwise clears the
		525	exception object.
		526
		527	The exception object will be thrown "as is" with the specified scalar in
		528	C<$@>, i.e. if it is a string, no line number or newline will be appended
		529	(unlike with C<die>).
		530
		531	This can be used as a softer means than C<cancel> to ask a coroutine to
		532	end itself, although there is no guarentee that the exception will lead to
		533	termination, and if the exception isn't caught it might well end the whole
		534	program.
		535
344	=cut	536	=cut
345		537
346	sub desc {	538	sub desc {
347	my $old = $_[0]{desc};	539	my $old = $_[0]{desc};
348	$_[0]{desc} = $_[1] if @_ > 1;	540	$_[0]{desc} = $_[1] if @_ > 1;
349	$old;	541	$old;
350	}	542	}
351		543
352	=back	544	=back
353		545
354	=head2 UTILITY FUNCTIONS	546	=head2 GLOBAL FUNCTIONS
355		547
356	=over 4	548	=over 4
357		549
		550	=item Coro::nready
		551
		552	Returns the number of coroutines that are currently in the ready state,
		553	i.e. that can be switched to by calling C<schedule> directory or
		554	indirectly. The value C<0> means that the only runnable coroutine is the
		555	currently running one, so C<cede> would have no effect, and C<schedule>
		556	would cause a deadlock unless there is an idle handler that wakes up some
		557	coroutines.
		558
		559	=item my $guard = Coro::guard { ... }
		560
		561	This creates and returns a guard object. Nothing happens until the object
		562	gets destroyed, in which case the codeblock given as argument will be
		563	executed. This is useful to free locks or other resources in case of a
		564	runtime error or when the coroutine gets canceled, as in both cases the
		565	guard block will be executed. The guard object supports only one method,
		566	C<< ->cancel >>, which will keep the codeblock from being executed.
		567
		568	Example: set some flag and clear it again when the coroutine gets canceled
		569	or the function returns:
		570
		571	sub do_something {
		572	my $guard = Coro::guard { $busy = 0 };
		573	$busy = 1;
		574
		575	# do something that requires $busy to be true
		576	}
		577
		578	=cut
		579
		580	sub guard(&) {
		581	bless \(my $cb = $_[0]), "Coro::guard"
		582	}
		583
		584	sub Coro::guard::cancel {
		585	${$_[0]} = sub { };
		586	}
		587
		588	sub Coro::guard::DESTROY {
		589	${$_[0]}->();
		590	}
		591
		592
358	=item unblock_sub { ... }	593	=item unblock_sub { ... }
359		594
360	This utility function takes a BLOCK or code reference and "unblocks" it,	595	This utility function takes a BLOCK or code reference and "unblocks" it,
361	returning the new coderef. This means that the new coderef will return	596	returning a new coderef. Unblocking means that calling the new coderef
362	immediately without blocking, returning nothing, while the original code	597	will return immediately without blocking, returning nothing, while the
363	ref will be called (with parameters) from within its own coroutine.	598	original code ref will be called (with parameters) from within another
		599	coroutine.
364		600
365	The reason this fucntion exists is that many event libraries (such as the	601	The reason this function exists is that many event libraries (such as the
366	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	602	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
367	of thread-safety). This means you must not block within event callbacks,	603	of thread-safety). This means you must not block within event callbacks,
368	otherwise you might suffer from crashes or worse.	604	otherwise you might suffer from crashes or worse. The only event library
		605	currently known that is safe to use without C<unblock_sub> is L<EV>.
369		606
370	This function allows your callbacks to block by executing them in another	607	This function allows your callbacks to block by executing them in another
371	coroutine where it is safe to block. One example where blocking is handy	608	coroutine where it is safe to block. One example where blocking is handy
372	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	609	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
373	disk.	610	disk, for example.
374		611
375	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	612	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
376	creating event callbacks that want to block.	613	creating event callbacks that want to block.
377		614
378	=cut	615	If your handler does not plan to block (e.g. simply sends a message to
		616	another coroutine, or puts some other coroutine into the ready queue),
		617	there is no reason to use C<unblock_sub>.
379		618
380	our @unblock_pool;	619	Note that you also need to use C<unblock_sub> for any other callbacks that
		620	are indirectly executed by any C-based event loop. For example, when you
		621	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		622	provides callbacks that are the result of some event callback, then you
		623	must not block either, or use C<unblock_sub>.
		624
		625	=cut
		626
381	our @unblock_queue;	627	our @unblock_queue;
382	our $UNBLOCK_POOL_SIZE = 2;
383		628
384	sub unblock_handler_ {	629	# we create a special coro because we want to cede,
385	while () {	630	# to reduce pressure on the coro pool (because most callbacks
386	my ($cb, @arg) = @{ delete $Coro::current->{arg} };	631	# return immediately and can be reused) and because we cannot cede
387	$cb->(@arg);	632	# inside an event callback.
388
389	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
390	push @unblock_pool, $Coro::current;
391	schedule;
392	}
393	}
394
395	our $unblock_scheduler = async {	633	our $unblock_scheduler = new Coro sub {
396	while () {	634	while () {
397	while (my $cb = pop @unblock_queue) {	635	while (my $cb = pop @unblock_queue) {
398	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);	636	# this is an inlined copy of async_pool
399	$handler->{arg} = $cb;	637	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		638
		639	$coro->{_invoke} = $cb;
400	$handler->ready;	640	$coro->ready;
401	cede;	641	cede; # for short-lived callbacks, this reduces pressure on the coro pool
402	}	642	}
403		643	schedule; # sleep well
404	schedule;
405	}	644	}
406	};	645	};
		646	$unblock_scheduler->desc ("[unblock_sub scheduler]");
407		647
408	sub unblock_sub(&) {	648	sub unblock_sub(&) {
409	my $cb = shift;	649	my $cb = shift;
410		650
411	sub {	651	sub {
412	push @unblock_queue, [$cb, @_];	652	unshift @unblock_queue, [$cb, @_];
413	$unblock_scheduler->ready;	653	$unblock_scheduler->ready;
414	}	654	}
415	}	655	}
416		656
417	=back	657	=back
…		…
420		660
421	1;	661	1;
422		662
423	=head1 BUGS/LIMITATIONS	663	=head1 BUGS/LIMITATIONS
424		664
425	- you must make very sure that no coro is still active on global
426	destruction. very bad things might happen otherwise (usually segfaults).
427
428	- this module is not thread-safe. You should only ever use this module	665	This module is not perl-pseudo-thread-safe. You should only ever use this
429	from the same thread (this requirement might be losened in the future	666	module from the same thread (this requirement might be removed in the
430	to allow per-thread schedulers, but Coro::State does not yet allow	667	future to allow per-thread schedulers, but Coro::State does not yet allow
431	this).	668	this). I recommend disabling thread support and using processes, as this
		669	is much faster and uses less memory.
432		670
433	=head1 SEE ALSO	671	=head1 SEE ALSO
434		672
		673	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		674
		675	Debugging: L<Coro::Debug>.
		676
435	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	677	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
436		678
437	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	679	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
438		680
439	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	681	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
440		682
441	Embedding: L<Coro:MakeMaker>	683	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		684
		685	XS API: L<Coro::MakeMaker>.
		686
		687	Low level Configuration, Coroutine Environment: L<Coro::State>.
442		688
443	=head1 AUTHOR	689	=head1 AUTHOR
444		690
445	Marc Lehmann <schmorp@schmorp.de>	691	Marc Lehmann <schmorp@schmorp.de>
446	http://home.schmorp.de/	692	http://home.schmorp.de/

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Revision 1.92 by root, Fri Dec 1 03:47:55 2006 UTC vs.
Revision 1.195 by root, Wed Jul 23 22:15:25 2008 UTC