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

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.92 by root, Fri Dec 1 03:47:55 2006 UTC vs.
Revision 1.181 by root, Fri May 9 22:04:37 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, such as multiple HTTP-GET requests
		41	running concurrently.
		42
		43	Coroutines are also useful because Perl has no support for threads (the so
		44	called "threads" that perl offers are nothing more than the (bad) process
		45	emulation coming from the Windows platform: On standard operating systems
		46	they serve no purpose whatsoever, except by making your programs slow and
		47	making them use a lot of memory. Best disable them when building perl, or
		48	aks your software vendor/distributor to do it for you).
		49
26	In this module, coroutines are defined as "callchain + lexical variables	50	In this module, coroutines are defined as "callchain + lexical variables +
27	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own	51	@_ + $_ + $@ + $/ + 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	52	its own set of lexicals and its own set of perls most important global
29	important global variables.	53	variables (see L<Coro::State> for more configuration).
30		54
31	=cut	55	=cut
32		56
33	package Coro;	57	package Coro;
34		58
…		…
41		65
42	our $idle; # idle handler	66	our $idle; # idle handler
43	our $main; # main coroutine	67	our $main; # main coroutine
44	our $current; # current coroutine	68	our $current; # current coroutine
45		69
46	our $VERSION = '3.0';	70	our $VERSION = 4.6;
47		71
48	our @EXPORT = qw(async cede schedule terminate current unblock_sub);	72	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
49	our %EXPORT_TAGS = (	73	our %EXPORT_TAGS = (
50	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	74	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51	);	75	);
52	our @EXPORT_OK = @{$EXPORT_TAGS{prio}};	76	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		77
88	=over 4	78	=over 4
89		79
90	=item $main	80	=item $Coro::main
91		81
92	This coroutine represents the main program.	82	This variable stores the coroutine object that represents the main
		83	program. While you cna C<ready> it and do most other things you can do to
		84	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		85	wether you are running in the main program or not.
93		86
94	=cut	87	=cut
95		88
96	$main = new Coro;	89	$main = new Coro;
97		90
98	=item $current (or as function: current)	91	=item $Coro::current
99		92
100	The current coroutine (the last coroutine switched to). The initial value	93	The coroutine object representing the current coroutine (the last
		94	coroutine that the Coro scheduler switched to). The initial value is
101	is C<$main> (of course).	95	C<$main> (of course).
102		96
103	This variable is B<strictly> I<read-only>. It is provided for performance	97	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	98	value stored in it and use it as any other coroutine object, but you must
105	C<Coro::current> function instead.	99	not otherwise modify the variable itself.
106		100
107	=cut	101	=cut
		102
		103	$main->{desc} = "[main::]";
108		104
109	# maybe some other module used Coro::Specific before...	105	# maybe some other module used Coro::Specific before...
110	if ($current) {
111	$main->{specific} = $current->{specific};	106	$main->{_specific} = $current->{_specific}
112	}	107	if $current;
113		108
114	$current = $main;	109	_set_current $main;
115		110
116	sub current() { $current }	111	sub current() { $current } # [DEPRECATED]
117		112
118	=item $idle	113	=item $Coro::idle
119		114
120	A callback that is called whenever the scheduler finds no ready coroutines	115	This variable is mainly useful to integrate Coro into event loops. It is
121	to run. The default implementation prints "FATAL: deadlock detected" and	116	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.	117	pretty low-level functionality.
		118
		119	This variable stores a callback that is called whenever the scheduler
		120	finds no ready coroutines to run. The default implementation prints
		121	"FATAL: deadlock detected" and exits, because the program has no other way
		122	to continue.
123		123
124	This hook is overwritten by modules such as C<Coro::Timer> and	124	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	125	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
126	coroutine so the scheduler can run it.	126	coroutine so the scheduler can run it.
127		127
		128	Note that the callback I<must not>, under any circumstances, block
		129	the current coroutine. Normally, this is achieved by having an "idle
		130	coroutine" that calls the event loop and then blocks again, and then
		131	readying that coroutine in the idle handler.
		132
		133	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		134	technique.
		135
128	Please note that if your callback recursively invokes perl (e.g. for event	136	Please note that if your callback recursively invokes perl (e.g. for event
129	handlers), then it must be prepared to be called recursively.	137	handlers), then it must be prepared to be called recursively itself.
130		138
131	=cut	139	=cut
132		140
133	$idle = sub {	141	$idle = sub {
134	print STDERR "FATAL: deadlock detected\n";	142	require Carp;
135	exit (51);	143	Carp::croak ("FATAL: deadlock detected");
136	};	144	};
		145
		146	sub _cancel {
		147	my ($self) = @_;
		148
		149	# free coroutine data and mark as destructed
		150	$self->_destroy
		151	or return;
		152
		153	# call all destruction callbacks
		154	$_->(@{$self->{_status}})
		155	for @{(delete $self->{_on_destroy}) \|\| []};
		156	}
137		157
138	# this coroutine is necessary because a coroutine	158	# this coroutine is necessary because a coroutine
139	# cannot destroy itself.	159	# cannot destroy itself.
140	my @destroy;	160	my @destroy;
		161	my $manager;
		162
141	my $manager; $manager = new Coro sub {	163	$manager = new Coro sub {
142	while () {	164	while () {
143	# by overwriting the state object with the manager we destroy it	165	(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) {	166	while @destroy;
149	my $coro = pop @destroy;
150	$coro->{status} \|\|= [];
151	$_->ready for @{delete $coro->{join} \|\| []};
152		167
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;	168	&schedule;
160	}	169	}
161	};	170	};
162		171	$manager->desc ("[coro manager]");
163	# static methods. not really.	172	$manager->prio (PRIO_MAX);
164		173
165	=back	174	=back
166		175
167	=head2 STATIC METHODS	176	=head2 SIMPLE COROUTINE CREATION
168
169	Static methods are actually functions that operate on the current coroutine only.
170		177
171	=over 4	178	=over 4
172		179
173	=item async { ... } [@args...]	180	=item async { ... } [@args...]
174		181
175	Create a new asynchronous coroutine and return it's coroutine object	182	Create a new coroutine and return it's coroutine object (usually
176	(usually unused). When the sub returns the new coroutine is automatically	183	unused). The coroutine will be put into the ready queue, so
		184	it will start running automatically on the next scheduler run.
		185
		186	The first argument is a codeblock/closure that should be executed in the
		187	coroutine. When it returns argument returns the coroutine is automatically
177	terminated.	188	terminated.
178		189
179	Calling C<exit> in a coroutine will not work correctly, so do not do that.	190	The remaining arguments are passed as arguments to the closure.
180		191
181	When the coroutine dies, the program will exit, just as in the main	192	See the C<Coro::State::new> constructor for info about the coroutine
182	program.	193	environment in which coroutines are executed.
183		194
		195	Calling C<exit> in a coroutine will do the same as calling exit outside
		196	the coroutine. Likewise, when the coroutine dies, the program will exit,
		197	just as it would in the main program.
		198
		199	If you do not want that, you can provide a default C<die> handler, or
		200	simply avoid dieing (by use of C<eval>).
		201
184	# create a new coroutine that just prints its arguments	202	Example: Create a new coroutine that just prints its arguments.
		203
185	async {	204	async {
186	print "@_\n";	205	print "@_\n";
187	} 1,2,3,4;	206	} 1,2,3,4;
188		207
189	=cut	208	=cut
190		209
191	sub async(&@) {	210	sub async(&@) {
192	my $pid = new Coro @_;	211	my $coro = new Coro @_;
193	$pid->ready;	212	$coro->ready;
194	$pid	213	$coro
195	}	214	}
		215
		216	=item async_pool { ... } [@args...]
		217
		218	Similar to C<async>, but uses a coroutine pool, so you should not call
		219	terminate or join on it (although you are allowed to), and you get a
		220	coroutine that might have executed other code already (which can be good
		221	or bad :).
		222
		223	On the plus side, this function is faster than creating (and destroying)
		224	a completely new coroutine, so if you need a lot of generic coroutines in
		225	quick successsion, use C<async_pool>, not C<async>.
		226
		227	The code block is executed in an C<eval> context and a warning will be
		228	issued in case of an exception instead of terminating the program, as
		229	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		230	will not work in the expected way, unless you call terminate or cancel,
		231	which somehow defeats the purpose of pooling (but is fine in the
		232	exceptional case).
		233
		234	The priority will be reset to C<0> after each run, tracing will be
		235	disabled, the description will be reset and the default output filehandle
		236	gets restored, so you can change all these. Otherwise the coroutine will
		237	be re-used "as-is": most notably if you change other per-coroutine global
		238	stuff such as C<$/> you I<must needs> to revert that change, which is most
		239	simply done by using local as in: C< local $/ >.
		240
		241	The pool size is limited to C<8> idle coroutines (this can be adjusted by
		242	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		243	required.
		244
		245	If you are concerned about pooled coroutines growing a lot because a
		246	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		247	{ terminate }> once per second or so to slowly replenish the pool. In
		248	addition to that, when the stacks used by a handler grows larger than 16kb
		249	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		250
		251	=cut
		252
		253	our $POOL_SIZE = 8;
		254	our $POOL_RSS = 16 * 1024;
		255	our @async_pool;
		256
		257	sub pool_handler {
		258	my $cb;
		259
		260	while () {
		261	eval {
		262	while () {
		263	_pool_1 $cb;
		264	&$cb;
		265	_pool_2 $cb;
		266	&schedule;
		267	}
		268	};
		269
		270	last if $@ eq "\3async_pool terminate\2\n";
		271	warn $@ if $@;
		272	}
		273	}
		274
		275	sub async_pool(&@) {
		276	# this is also inlined into the unlock_scheduler
		277	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		278
		279	$coro->{_invoke} = [@_];
		280	$coro->ready;
		281
		282	$coro
		283	}
		284
		285	=back
		286
		287	=head2 STATIC METHODS
		288
		289	Static methods are actually functions that operate on the current coroutine.
		290
		291	=over 4
196		292
197	=item schedule	293	=item schedule
198		294
199	Calls the scheduler. Please note that the current coroutine will not be put	295	Calls the scheduler. The scheduler will find the next coroutine that is
		296	to be run from the ready queue and switches to it. The next coroutine
		297	to be run is simply the one with the highest priority that is longest
		298	in its ready queue. If there is no coroutine ready, it will clal the
		299	C<$Coro::idle> hook.
		300
		301	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	302	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	303	again unless something else (e.g. an event handler) calls C<< ->ready >>,
202	ready.	304	thus waking you up.
		305
		306	This makes C<schedule> I<the> generic method to use to block the current
		307	coroutine and wait for events: first you remember the current coroutine in
		308	a variable, then arrange for some callback of yours to call C<< ->ready
		309	>> on that once some event happens, and last you call C<schedule> to put
		310	yourself to sleep. Note that a lot of things can wake your coroutine up,
		311	so you need to check wether the event indeed happened, e.g. by storing the
		312	status in a variable.
203		313
204	The canonical way to wait on external events is this:	314	The canonical way to wait on external events is this:
205		315
206	{	316	{
207	# remember current coroutine	317	# remember current coroutine
…		…
212	# wake up sleeping coroutine	322	# wake up sleeping coroutine
213	$current->ready;	323	$current->ready;
214	undef $current;	324	undef $current;
215	};	325	};
216		326
217	# call schedule until event occured.	327	# call schedule until event occurred.
218	# in case we are woken up for other reasons	328	# in case we are woken up for other reasons
219	# (current still defined), loop.	329	# (current still defined), loop.
220	Coro::schedule while $current;	330	Coro::schedule while $current;
221	}	331	}
222		332
223	=item cede	333	=item cede
224		334
225	"Cede" to other coroutines. This function puts the current coroutine into the	335	"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	336	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.	337	up the current "timeslice" to other coroutines of the same or higher
		338	priority. Once your coroutine gets its turn again it will automatically be
		339	resumed.
		340
		341	This function is often called C<yield> in other languages.
		342
		343	=item Coro::cede_notself
		344
		345	Works like cede, but is not exported by default and will cede to I<any>
		346	coroutine, regardless of priority. This is useful sometimes to ensure
		347	progress is made.
228		348
229	=item terminate [arg...]	349	=item terminate [arg...]
230		350
231	Terminates the current coroutine with the given status values (see L<cancel>).	351	Terminates the current coroutine with the given status values (see L<cancel>).
		352
		353	=item killall
		354
		355	Kills/terminates/cancels all coroutines except the currently running
		356	one. This is useful after a fork, either in the child or the parent, as
		357	usually only one of them should inherit the running coroutines.
		358
		359	Note that while this will try to free some of the main programs resources,
		360	you cnanot free all of them, so if a coroutine that is not the main
		361	program calls this function, there will be some one-time resource leak.
232		362
233	=cut	363	=cut
234		364
235	sub terminate {	365	sub terminate {
236	$current->cancel (@_);	366	$current->cancel (@_);
237	}	367	}
238		368
		369	sub killall {
		370	for (Coro::State::list) {
		371	$_->cancel
		372	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		373	}
		374	}
		375
239	=back	376	=back
240		377
241	# dynamic methods
242
243	=head2 COROUTINE METHODS	378	=head2 COROUTINE METHODS
244		379
245	These are the methods you can call on coroutine objects.	380	These are the methods you can call on coroutine objects (or to create
		381	them).
246		382
247	=over 4	383	=over 4
248		384
249	=item new Coro \&sub [, @args...]	385	=item new Coro \&sub [, @args...]
250		386
251	Create a new coroutine and return it. When the sub returns the coroutine	387	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	388	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	389	called. To make the coroutine run you must first put it into the ready
254	by calling the ready method.	390	queue by calling the ready method.
255		391
256	Calling C<exit> in a coroutine will not work correctly, so do not do that.	392	See C<async> and C<Coro::State::new> for additional info about the
		393	coroutine environment.
257		394
258	=cut	395	=cut
259		396
260	sub _new_coro {	397	sub _run_coro {
261	terminate &{+shift};	398	terminate &{+shift};
262	}	399	}
263		400
264	sub new {	401	sub new {
265	my $class = shift;	402	my $class = shift;
266		403
267	$class->SUPER::new (\&_new_coro, @_)	404	$class->SUPER::new (\&_run_coro, @_)
268	}	405	}
269		406
270	=item $success = $coroutine->ready	407	=item $success = $coroutine->ready
271		408
272	Put the given coroutine into the ready queue (according to it's priority)	409	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	410	queue for each priority) and return true. If the coroutine is already in
274	and return false.	411	the ready queue, do nothing and return false.
		412
		413	This ensures that the scheduler will resume this coroutine automatically
		414	once all the coroutines of higher priority and all coroutines of the same
		415	priority that were put into the ready queue earlier have been resumed.
275		416
276	=item $is_ready = $coroutine->is_ready	417	=item $is_ready = $coroutine->is_ready
277		418
278	Return wether the coroutine is currently the ready queue or not,	419	Return wether the coroutine is currently the ready queue or not,
279		420
280	=item $coroutine->cancel (arg...)	421	=item $coroutine->cancel (arg...)
281		422
282	Terminates the given coroutine and makes it return the given arguments as	423	Terminates the given coroutine and makes it return the given arguments as
283	status (default: the empty list).	424	status (default: the empty list). Never returns if the coroutine is the
		425	current coroutine.
284		426
285	=cut	427	=cut
286		428
287	sub cancel {	429	sub cancel {
288	my $self = shift;	430	my $self = shift;
289	$self->{status} = [@_];	431	$self->{_status} = [@_];
		432
		433	if ($current == $self) {
290	push @destroy, $self;	434	push @destroy, $self;
291	$manager->ready;	435	$manager->ready;
292	&schedule if $current == $self;	436	&schedule while 1;
		437	} else {
		438	$self->_cancel;
		439	}
293	}	440	}
294		441
295	=item $coroutine->join	442	=item $coroutine->join
296		443
297	Wait until the coroutine terminates and return any values given to the	444	Wait until the coroutine terminates and return any values given to the
298	C<terminate> or C<cancel> functions. C<join> can be called multiple times	445	C<terminate> or C<cancel> functions. C<join> can be called concurrently
299	from multiple coroutine.	446	from multiple coroutines, and all will be resumed and given the status
		447	return once the C<$coroutine> terminates.
300		448
301	=cut	449	=cut
302		450
303	sub join {	451	sub join {
304	my $self = shift;	452	my $self = shift;
		453
305	unless ($self->{status}) {	454	unless ($self->{_status}) {
306	push @{$self->{join}}, $current;	455	my $current = $current;
307	&schedule;	456
		457	push @{$self->{_on_destroy}}, sub {
		458	$current->ready;
		459	undef $current;
		460	};
		461
		462	&schedule while $current;
308	}	463	}
		464
309	wantarray ? @{$self->{status}} : $self->{status}[0];	465	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		466	}
		467
		468	=item $coroutine->on_destroy (\&cb)
		469
		470	Registers a callback that is called when this coroutine gets destroyed,
		471	but before it is joined. The callback gets passed the terminate arguments,
		472	if any, and I<must not> die, under any circumstances.
		473
		474	=cut
		475
		476	sub on_destroy {
		477	my ($self, $cb) = @_;
		478
		479	push @{ $self->{_on_destroy} }, $cb;
310	}	480	}
311		481
312	=item $oldprio = $coroutine->prio ($newprio)	482	=item $oldprio = $coroutine->prio ($newprio)
313		483
314	Sets (or gets, if the argument is missing) the priority of the	484	Sets (or gets, if the argument is missing) the priority of the
…		…
339	=item $olddesc = $coroutine->desc ($newdesc)	509	=item $olddesc = $coroutine->desc ($newdesc)
340		510
341	Sets (or gets in case the argument is missing) the description for this	511	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.	512	coroutine. This is just a free-form string you can associate with a coroutine.
343		513
		514	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
		515	can modify this member directly if you wish.
		516
		517	=item $coroutine->throw ([$scalar])
		518
		519	If C<$throw> is specified and defined, it will be thrown as an exception
		520	inside the coroutine at the next convinient point in time (usually after
		521	it gains control at the next schedule/transfer/cede). Otherwise clears the
		522	exception object.
		523
		524	The exception object will be thrown "as is" with the specified scalar in
		525	C<$@>, i.e. if it is a string, no line number or newline will be appended
		526	(unlike with C<die>).
		527
		528	This can be used as a softer means than C<cancel> to ask a coroutine to
		529	end itself, although there is no guarentee that the exception will lead to
		530	termination, and if the exception isn't caught it might well end the whole
		531	program.
		532
344	=cut	533	=cut
345		534
346	sub desc {	535	sub desc {
347	my $old = $_[0]{desc};	536	my $old = $_[0]{desc};
348	$_[0]{desc} = $_[1] if @_ > 1;	537	$_[0]{desc} = $_[1] if @_ > 1;
349	$old;	538	$old;
350	}	539	}
351		540
352	=back	541	=back
353		542
354	=head2 UTILITY FUNCTIONS	543	=head2 GLOBAL FUNCTIONS
355		544
356	=over 4	545	=over 4
357		546
		547	=item Coro::nready
		548
		549	Returns the number of coroutines that are currently in the ready state,
		550	i.e. that can be switched to by calling C<schedule> directory or
		551	indirectly. The value C<0> means that the only runnable coroutine is the
		552	currently running one, so C<cede> would have no effect, and C<schedule>
		553	would cause a deadlock unless there is an idle handler that wakes up some
		554	coroutines.
		555
		556	=item my $guard = Coro::guard { ... }
		557
		558	This creates and returns a guard object. Nothing happens until the object
		559	gets destroyed, in which case the codeblock given as argument will be
		560	executed. This is useful to free locks or other resources in case of a
		561	runtime error or when the coroutine gets canceled, as in both cases the
		562	guard block will be executed. The guard object supports only one method,
		563	C<< ->cancel >>, which will keep the codeblock from being executed.
		564
		565	Example: set some flag and clear it again when the coroutine gets canceled
		566	or the function returns:
		567
		568	sub do_something {
		569	my $guard = Coro::guard { $busy = 0 };
		570	$busy = 1;
		571
		572	# do something that requires $busy to be true
		573	}
		574
		575	=cut
		576
		577	sub guard(&) {
		578	bless \(my $cb = $_[0]), "Coro::guard"
		579	}
		580
		581	sub Coro::guard::cancel {
		582	${$_[0]} = sub { };
		583	}
		584
		585	sub Coro::guard::DESTROY {
		586	${$_[0]}->();
		587	}
		588
		589
358	=item unblock_sub { ... }	590	=item unblock_sub { ... }
359		591
360	This utility function takes a BLOCK or code reference and "unblocks" it,	592	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	593	returning a new coderef. Unblocking means that calling the new coderef
362	immediately without blocking, returning nothing, while the original code	594	will return immediately without blocking, returning nothing, while the
363	ref will be called (with parameters) from within its own coroutine.	595	original code ref will be called (with parameters) from within another
		596	coroutine.
364		597
365	The reason this fucntion exists is that many event libraries (such as the	598	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	599	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,	600	of thread-safety). This means you must not block within event callbacks,
368	otherwise you might suffer from crashes or worse.	601	otherwise you might suffer from crashes or worse. The only event library
		602	currently known that is safe to use without C<unblock_sub> is L<EV>.
369		603
370	This function allows your callbacks to block by executing them in another	604	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	605	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	606	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
373	disk.	607	disk, for example.
374		608
375	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	609	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
376	creating event callbacks that want to block.	610	creating event callbacks that want to block.
377		611
378	=cut	612	If your handler does not plan to block (e.g. simply sends a message to
		613	another coroutine, or puts some other coroutine into the ready queue),
		614	there is no reason to use C<unblock_sub>.
379		615
380	our @unblock_pool;	616	=cut
		617
381	our @unblock_queue;	618	our @unblock_queue;
382	our $UNBLOCK_POOL_SIZE = 2;
383		619
384	sub unblock_handler_ {	620	# we create a special coro because we want to cede,
385	while () {	621	# to reduce pressure on the coro pool (because most callbacks
386	my ($cb, @arg) = @{ delete $Coro::current->{arg} };	622	# return immediately and can be reused) and because we cannot cede
387	$cb->(@arg);	623	# 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 {	624	our $unblock_scheduler = new Coro sub {
396	while () {	625	while () {
397	while (my $cb = pop @unblock_queue) {	626	while (my $cb = pop @unblock_queue) {
398	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);	627	# this is an inlined copy of async_pool
399	$handler->{arg} = $cb;	628	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		629
		630	$coro->{_invoke} = $cb;
400	$handler->ready;	631	$coro->ready;
401	cede;	632	cede; # for short-lived callbacks, this reduces pressure on the coro pool
402	}	633	}
403		634	schedule; # sleep well
404	schedule;
405	}	635	}
406	};	636	};
		637	$unblock_scheduler->desc ("[unblock_sub scheduler]");
407		638
408	sub unblock_sub(&) {	639	sub unblock_sub(&) {
409	my $cb = shift;	640	my $cb = shift;
410		641
411	sub {	642	sub {
412	push @unblock_queue, [$cb, @_];	643	unshift @unblock_queue, [$cb, @_];
413	$unblock_scheduler->ready;	644	$unblock_scheduler->ready;
414	}	645	}
415	}	646	}
416		647
417	=back	648	=back
…		…
420		651
421	1;	652	1;
422		653
423	=head1 BUGS/LIMITATIONS	654	=head1 BUGS/LIMITATIONS
424		655
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	656	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	657	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	658	future to allow per-thread schedulers, but Coro::State does not yet allow
431	this).	659	this). I recommend disabling thread support and using processes, as this
		660	is much faster and uses less memory.
432		661
433	=head1 SEE ALSO	662	=head1 SEE ALSO
434		663
		664	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		665
		666	Debugging: L<Coro::Debug>.
		667
435	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	668	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
436		669
437	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	670	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
438		671
439	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	672	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
440		673
441	Embedding: L<Coro:MakeMaker>	674	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		675
		676	XS API: L<Coro::MakeMaker>.
		677
		678	Low level Configuration, Coroutine Environment: L<Coro::State>.
442		679
443	=head1 AUTHOR	680	=head1 AUTHOR
444		681
445	Marc Lehmann <schmorp@schmorp.de>	682	Marc Lehmann <schmorp@schmorp.de>
446	http://home.schmorp.de/	683	http://home.schmorp.de/

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Revision 1.181 by root, Fri May 9 22:04:37 2008 UTC