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

Comparing Coro/Coro.pm (file contents):
Revision 1.100 by root, Tue Dec 12 13:56:45 2006 UTC vs.
Revision 1.229 by root, Thu Nov 20 06:32:55 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	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	This module collection manages coroutines. Coroutines are similar to
24	to threads but don't run in parallel at the same time even on SMP	32	threads but don't (in general) run in parallel at the same time even
25	machines. The specific flavor of coroutine use din this module also	33	on SMP machines. The specific flavor of coroutine used in this module
26	guarentees you that it will not switch between coroutines unless	34	also guarantees you that it will not switch between coroutines unless
27	necessary, at easily-identified points in your program, so locking and	35	necessary, at easily-identified points in your program, so locking and
28	parallel access are rarely an issue, making coroutine programming much	36	parallel access are rarely an issue, making coroutine programming much
29	safer than threads programming.	37	safer and easier than threads programming.
30		38
31	(Perl, however, does not natively support real threads but instead does a	39	Unlike a normal perl program, however, coroutines allow you to have
32	very slow and memory-intensive emulation of processes using threads. This	40	multiple running interpreters that share data, which is especially useful
33	is a performance win on Windows machines, and a loss everywhere else).	41	to code pseudo-parallel processes and for event-based programming, such as
		42	multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to
		43	learn more.
		44
		45	Coroutines are also useful because Perl has no support for threads (the so
		46	called "threads" that perl offers are nothing more than the (bad) process
		47	emulation coming from the Windows platform: On standard operating systems
		48	they serve no purpose whatsoever, except by making your programs slow and
		49	making them use a lot of memory. Best disable them when building perl, or
		50	aks your software vendor/distributor to do it for you).
34		51
35	In this module, coroutines are defined as "callchain + lexical variables +	52	In this module, coroutines are defined as "callchain + lexical variables +
36	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	53	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
37	its own set of lexicals and its own set of perls most important global	54	its own set of lexicals and its own set of perls most important global
38	variables.	55	variables (see L<Coro::State> for more configuration).
39		56
40	=cut	57	=cut
41		58
42	package Coro;	59	package Coro;
43		60
44	use strict;	61	use strict qw(vars subs);
45	no warnings "uninitialized";	62	no warnings "uninitialized";
46		63
47	use Coro::State;	64	use Coro::State;
48		65
49	use base qw(Coro::State Exporter);	66	use base qw(Coro::State Exporter);
50		67
51	our $idle; # idle handler	68	our $idle; # idle handler
52	our $main; # main coroutine	69	our $main; # main coroutine
53	our $current; # current coroutine	70	our $current; # current coroutine
54		71
55	our $VERSION = '3.2';	72	our $VERSION = 5.0;
56		73
57	our @EXPORT = qw(async cede schedule terminate current unblock_sub);	74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
58	our %EXPORT_TAGS = (	75	our %EXPORT_TAGS = (
59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60	);	77	);
61	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	78	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
62		79
63	{
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
97	=over 4	80	=over 4
98		81
99	=item $main	82	=item $Coro::main
100		83
101	This coroutine represents the main program.	84	This variable stores the coroutine object that represents the main
		85	program. While you cna C<ready> it and do most other things you can do to
		86	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		87	whether you are running in the main program or not.
102		88
103	=cut	89	=cut
104		90
105	$main = new Coro;	91	# $main is now being initialised by Coro::State
106		92
107	=item $current (or as function: current)	93	=item $Coro::current
108		94
109	The current coroutine (the last coroutine switched to). The initial value	95	The coroutine object representing the current coroutine (the last
		96	coroutine that the Coro scheduler switched to). The initial value is
110	is C<$main> (of course).	97	C<$Coro::main> (of course).
111		98
112	This variable is B<strictly> I<read-only>. It is provided for performance	99	This variable is B<strictly> I<read-only>. You can take copies of the
113	reasons. If performance is not essentiel you are encouraged to use the	100	value stored in it and use it as any other coroutine object, but you must
114	C<Coro::current> function instead.	101	not otherwise modify the variable itself.
115		102
116	=cut	103	=cut
117		104
118	# maybe some other module used Coro::Specific before...
119	$main->{specific} = $current->{specific}
120	if $current;
121
122	_set_current $main;
123
124	sub current() { $current }	105	sub current() { $current } # [DEPRECATED]
125		106
126	=item $idle	107	=item $Coro::idle
127		108
128	A callback that is called whenever the scheduler finds no ready coroutines	109	This variable is mainly useful to integrate Coro into event loops. It is
129	to run. The default implementation prints "FATAL: deadlock detected" and	110	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
130	exits, because the program has no other way to continue.	111	pretty low-level functionality.
		112
		113	This variable stores a callback that is called whenever the scheduler
		114	finds no ready coroutines to run. The default implementation prints
		115	"FATAL: deadlock detected" and exits, because the program has no other way
		116	to continue.
131		117
132	This hook is overwritten by modules such as C<Coro::Timer> and	118	This hook is overwritten by modules such as C<Coro::Timer> and
133	C<Coro::Event> to wait on an external event that hopefully wake up a	119	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
134	coroutine so the scheduler can run it.	120	coroutine so the scheduler can run it.
135		121
		122	Note that the callback I<must not>, under any circumstances, block
		123	the current coroutine. Normally, this is achieved by having an "idle
		124	coroutine" that calls the event loop and then blocks again, and then
		125	readying that coroutine in the idle handler.
		126
		127	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		128	technique.
		129
136	Please note that if your callback recursively invokes perl (e.g. for event	130	Please note that if your callback recursively invokes perl (e.g. for event
137	handlers), then it must be prepared to be called recursively.	131	handlers), then it must be prepared to be called recursively itself.
138		132
139	=cut	133	=cut
140		134
141	$idle = sub {	135	$idle = sub {
142	require Carp;	136	require Carp;
143	Carp::croak ("FATAL: deadlock detected");	137	Carp::croak ("FATAL: deadlock detected");
144	};	138	};
145		139
		140	sub _cancel {
		141	my ($self) = @_;
		142
		143	# free coroutine data and mark as destructed
		144	$self->_destroy
		145	or return;
		146
		147	# call all destruction callbacks
		148	$_->(@{$self->{_status}})
		149	for @{ delete $self->{_on_destroy} \|\| [] };
		150	}
		151
146	# this coroutine is necessary because a coroutine	152	# this coroutine is necessary because a coroutine
147	# cannot destroy itself.	153	# cannot destroy itself.
148	my @destroy;	154	our @destroy;
		155	our $manager;
		156
149	my $manager; $manager = new Coro sub {	157	$manager = new Coro sub {
150	while () {	158	while () {
151	# by overwriting the state object with the manager we destroy it	159	(shift @destroy)->_cancel
152	# while still being able to schedule this coroutine (in case it has
153	# been readied multiple times. this is harmless since the manager
154	# can be called as many times as neccessary and will always
155	# remove itself from the runqueue
156	while (@destroy) {	160	while @destroy;
157	my $coro = pop @destroy;
158	$coro->{status} \|\|= [];
159	$_->ready for @{delete $coro->{join} \|\| []};
160		161
161	# the next line destroys the coro state, but keeps the
162	# coroutine itself intact (we basically make it a zombie
163	# coroutine that always runs the manager thread, so it's possible
164	# to transfer() to this coroutine).
165	$coro->_clone_state_from ($manager);
166	}
167	&schedule;	162	&schedule;
168	}	163	}
169	};	164	};
170		165	$manager->{desc} = "[coro manager]";
171	# static methods. not really.	166	$manager->prio (PRIO_MAX);
172		167
173	=back	168	=back
174		169
175	=head2 STATIC METHODS	170	=head2 SIMPLE COROUTINE CREATION
176
177	Static methods are actually functions that operate on the current coroutine only.
178		171
179	=over 4	172	=over 4
180		173
181	=item async { ... } [@args...]	174	=item async { ... } [@args...]
182		175
183	Create a new asynchronous coroutine and return it's coroutine object	176	Create a new coroutine and return it's coroutine object (usually
184	(usually unused). When the sub returns the new coroutine is automatically	177	unused). The coroutine will be put into the ready queue, so
		178	it will start running automatically on the next scheduler run.
		179
		180	The first argument is a codeblock/closure that should be executed in the
		181	coroutine. When it returns argument returns the coroutine is automatically
185	terminated.	182	terminated.
186		183
187	Calling C<exit> in a coroutine will not work correctly, so do not do that.	184	The remaining arguments are passed as arguments to the closure.
188		185
189	When the coroutine dies, the program will exit, just as in the main	186	See the C<Coro::State::new> constructor for info about the coroutine
190	program.	187	environment in which coroutines are executed.
191		188
		189	Calling C<exit> in a coroutine will do the same as calling exit outside
		190	the coroutine. Likewise, when the coroutine dies, the program will exit,
		191	just as it would in the main program.
		192
		193	If you do not want that, you can provide a default C<die> handler, or
		194	simply avoid dieing (by use of C<eval>).
		195
192	# create a new coroutine that just prints its arguments	196	Example: Create a new coroutine that just prints its arguments.
		197
193	async {	198	async {
194	print "@_\n";	199	print "@_\n";
195	} 1,2,3,4;	200	} 1,2,3,4;
196		201
197	=cut	202	=cut
198		203
199	sub async(&@) {	204	sub async(&@) {
200	my $pid = new Coro @_;	205	my $coro = new Coro @_;
201	$pid->ready;	206	$coro->ready;
202	$pid	207	$coro
203	}	208	}
		209
		210	=item async_pool { ... } [@args...]
		211
		212	Similar to C<async>, but uses a coroutine pool, so you should not call
		213	terminate or join on it (although you are allowed to), and you get a
		214	coroutine that might have executed other code already (which can be good
		215	or bad :).
		216
		217	On the plus side, this function is about twice as fast as creating (and
		218	destroying) a completely new coroutine, so if you need a lot of generic
		219	coroutines in quick successsion, use C<async_pool>, not C<async>.
		220
		221	The code block is executed in an C<eval> context and a warning will be
		222	issued in case of an exception instead of terminating the program, as
		223	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		224	will not work in the expected way, unless you call terminate or cancel,
		225	which somehow defeats the purpose of pooling (but is fine in the
		226	exceptional case).
		227
		228	The priority will be reset to C<0> after each run, tracing will be
		229	disabled, the description will be reset and the default output filehandle
		230	gets restored, so you can change all these. Otherwise the coroutine will
		231	be re-used "as-is": most notably if you change other per-coroutine global
		232	stuff such as C<$/> you I<must needs> revert that change, which is most
		233	simply done by using local as in: C<< local $/ >>.
		234
		235	The idle pool size is limited to C<8> idle coroutines (this can be
		236	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		237	coros as required.
		238
		239	If you are concerned about pooled coroutines growing a lot because a
		240	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		241	{ terminate }> once per second or so to slowly replenish the pool. In
		242	addition to that, when the stacks used by a handler grows larger than 16kb
		243	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		244
		245	=cut
		246
		247	our $POOL_SIZE = 8;
		248	our $POOL_RSS = 16 * 1024;
		249	our @async_pool;
		250
		251	sub pool_handler {
		252	while () {
		253	eval {
		254	&{&_pool_handler} while 1;
		255	};
		256
		257	warn $@ if $@;
		258	}
		259	}
		260
		261	=back
		262
		263	=head2 STATIC METHODS
		264
		265	Static methods are actually functions that operate on the current coroutine.
		266
		267	=over 4
204		268
205	=item schedule	269	=item schedule
206		270
207	Calls the scheduler. Please note that the current coroutine will not be put	271	Calls the scheduler. The scheduler will find the next coroutine that is
		272	to be run from the ready queue and switches to it. The next coroutine
		273	to be run is simply the one with the highest priority that is longest
		274	in its ready queue. If there is no coroutine ready, it will clal the
		275	C<$Coro::idle> hook.
		276
		277	Please note that the current coroutine will I<not> be put into the ready
208	into the ready queue, so calling this function usually means you will	278	queue, so calling this function usually means you will never be called
209	never be called again unless something else (e.g. an event handler) calls	279	again unless something else (e.g. an event handler) calls C<< ->ready >>,
210	ready.	280	thus waking you up.
211		281
212	The canonical way to wait on external events is this:	282	This makes C<schedule> I<the> generic method to use to block the current
		283	coroutine and wait for events: first you remember the current coroutine in
		284	a variable, then arrange for some callback of yours to call C<< ->ready
		285	>> on that once some event happens, and last you call C<schedule> to put
		286	yourself to sleep. Note that a lot of things can wake your coroutine up,
		287	so you need to check whether the event indeed happened, e.g. by storing the
		288	status in a variable.
213		289
		290	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
		291
		292	=item cede
		293
		294	"Cede" to other coroutines. This function puts the current coroutine into
		295	the ready queue and calls C<schedule>, which has the effect of giving
		296	up the current "timeslice" to other coroutines of the same or higher
		297	priority. Once your coroutine gets its turn again it will automatically be
		298	resumed.
		299
		300	This function is often called C<yield> in other languages.
		301
		302	=item Coro::cede_notself
		303
		304	Works like cede, but is not exported by default and will cede to I<any>
		305	coroutine, regardless of priority. This is useful sometimes to ensure
		306	progress is made.
		307
		308	=item terminate [arg...]
		309
		310	Terminates the current coroutine with the given status values (see L<cancel>).
		311
		312	=item killall
		313
		314	Kills/terminates/cancels all coroutines except the currently running
		315	one. This is useful after a fork, either in the child or the parent, as
		316	usually only one of them should inherit the running coroutines.
		317
		318	Note that while this will try to free some of the main programs resources,
		319	you cannot free all of them, so if a coroutine that is not the main
		320	program calls this function, there will be some one-time resource leak.
		321
		322	=cut
		323
		324	sub terminate {
		325	$current->{_status} = [@_];
		326	push @destroy, $current;
		327	$manager->ready;
		328	do { &schedule } while 1;
		329	}
		330
		331	sub killall {
		332	for (Coro::State::list) {
		333	$_->cancel
		334	if $_ != $current && UNIVERSAL::isa $_, "Coro";
214	{	335	}
215	# remember current coroutine	336	}
		337
		338	=back
		339
		340	=head2 COROUTINE METHODS
		341
		342	These are the methods you can call on coroutine objects (or to create
		343	them).
		344
		345	=over 4
		346
		347	=item new Coro \&sub [, @args...]
		348
		349	Create a new coroutine and return it. When the sub returns, the coroutine
		350	automatically terminates as if C<terminate> with the returned values were
		351	called. To make the coroutine run you must first put it into the ready
		352	queue by calling the ready method.
		353
		354	See C<async> and C<Coro::State::new> for additional info about the
		355	coroutine environment.
		356
		357	=cut
		358
		359	sub _terminate {
		360	terminate &{+shift};
		361	}
		362
		363	=item $success = $coroutine->ready
		364
		365	Put the given coroutine into the end of its ready queue (there is one
		366	queue for each priority) and return true. If the coroutine is already in
		367	the ready queue, do nothing and return false.
		368
		369	This ensures that the scheduler will resume this coroutine automatically
		370	once all the coroutines of higher priority and all coroutines of the same
		371	priority that were put into the ready queue earlier have been resumed.
		372
		373	=item $is_ready = $coroutine->is_ready
		374
		375	Return whether the coroutine is currently the ready queue or not,
		376
		377	=item $coroutine->cancel (arg...)
		378
		379	Terminates the given coroutine and makes it return the given arguments as
		380	status (default: the empty list). Never returns if the coroutine is the
		381	current coroutine.
		382
		383	=cut
		384
		385	sub cancel {
		386	my $self = shift;
		387
		388	if ($current == $self) {
		389	terminate @_;
		390	} else {
		391	$self->{_status} = [@_];
		392	$self->_cancel;
		393	}
		394	}
		395
		396	=item $coroutine->schedule_to
		397
		398	Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
		399	of continuing with the next coro from the ready queue, always switch to
		400	the given coroutine object (regardless of priority etc.). The readyness
		401	state of that coroutine isn't changed.
		402
		403	This is an advanced method for special cases - I'd love to hear about any
		404	uses for this one.
		405
		406	=item $coroutine->cede_to
		407
		408	Like C<schedule_to>, but puts the current coroutine into the ready
		409	queue. This has the effect of temporarily switching to the given
		410	coroutine, and continuing some time later.
		411
		412	This is an advanced method for special cases - I'd love to hear about any
		413	uses for this one.
		414
		415	=item $coroutine->throw ([$scalar])
		416
		417	If C<$throw> is specified and defined, it will be thrown as an exception
		418	inside the coroutine at the next convenient point in time. Otherwise
		419	clears the exception object.
		420
		421	Coro will check for the exception each time a schedule-like-function
		422	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		423	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		424	detect this case and return early in case an exception is pending.
		425
		426	The exception object will be thrown "as is" with the specified scalar in
		427	C<$@>, i.e. if it is a string, no line number or newline will be appended
		428	(unlike with C<die>).
		429
		430	This can be used as a softer means than C<cancel> to ask a coroutine to
		431	end itself, although there is no guarantee that the exception will lead to
		432	termination, and if the exception isn't caught it might well end the whole
		433	program.
		434
		435	You might also think of C<throw> as being the moral equivalent of
		436	C<kill>ing a coroutine with a signal (in this case, a scalar).
		437
		438	=item $coroutine->join
		439
		440	Wait until the coroutine terminates and return any values given to the
		441	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		442	from multiple coroutines, and all will be resumed and given the status
		443	return once the C<$coroutine> terminates.
		444
		445	=cut
		446
		447	sub join {
		448	my $self = shift;
		449
		450	unless ($self->{_status}) {
216	my $current = $Coro::current;	451	my $current = $current;
217		452
218	# register a hypothetical event handler	453	push @{$self->{_on_destroy}}, sub {
219	on_event_invoke sub {
220	# wake up sleeping coroutine
221	$current->ready;	454	$current->ready;
222	undef $current;	455	undef $current;
223	};	456	};
224		457
225	# call schedule until event occured.
226	# in case we are woken up for other reasons
227	# (current still defined), loop.
228	Coro::schedule while $current;	458	&schedule while $current;
229	}	459	}
230		460
231	=item cede
232
233	"Cede" to other coroutines. This function puts the current coroutine into the
234	ready queue and calls C<schedule>, which has the effect of giving up the
235	current "timeslice" to other coroutines of the same or higher priority.
236
237	=item terminate [arg...]
238
239	Terminates the current coroutine with the given status values (see L<cancel>).
240
241	=cut
242
243	sub terminate {
244	$current->cancel (@_);
245	}
246
247	=back
248
249	# dynamic methods
250
251	=head2 COROUTINE METHODS
252
253	These are the methods you can call on coroutine objects.
254
255	=over 4
256
257	=item new Coro \&sub [, @args...]
258
259	Create a new coroutine and return it. When the sub returns the coroutine
260	automatically terminates as if C<terminate> with the returned values were
261	called. To make the coroutine run you must first put it into the ready queue
262	by calling the ready method.
263
264	Calling C<exit> in a coroutine will not work correctly, so do not do that.
265
266	=cut
267
268	sub _run_coro {
269	terminate &{+shift};
270	}
271
272	sub new {
273	my $class = shift;
274
275	$class->SUPER::new (\&_run_coro, @_)
276	}
277
278	=item $success = $coroutine->ready
279
280	Put the given coroutine into the ready queue (according to it's priority)
281	and return true. If the coroutine is already in the ready queue, do nothing
282	and return false.
283
284	=item $is_ready = $coroutine->is_ready
285
286	Return wether the coroutine is currently the ready queue or not,
287
288	=item $coroutine->cancel (arg...)
289
290	Terminates the given coroutine and makes it return the given arguments as
291	status (default: the empty list).
292
293	=cut
294
295	sub cancel {
296	my $self = shift;
297	$self->{status} = [@_];
298	push @destroy, $self;
299	$manager->ready;
300	&schedule if $current == $self;
301	}
302
303	=item $coroutine->join
304
305	Wait until the coroutine terminates and return any values given to the
306	C<terminate> or C<cancel> functions. C<join> can be called multiple times
307	from multiple coroutine.
308
309	=cut
310
311	sub join {
312	my $self = shift;
313	unless ($self->{status}) {
314	push @{$self->{join}}, $current;
315	&schedule;
316	}
317	wantarray ? @{$self->{status}} : $self->{status}[0];	461	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		462	}
		463
		464	=item $coroutine->on_destroy (\&cb)
		465
		466	Registers a callback that is called when this coroutine gets destroyed,
		467	but before it is joined. The callback gets passed the terminate arguments,
		468	if any, and I<must not> die, under any circumstances.
		469
		470	=cut
		471
		472	sub on_destroy {
		473	my ($self, $cb) = @_;
		474
		475	push @{ $self->{_on_destroy} }, $cb;
318	}	476	}
319		477
320	=item $oldprio = $coroutine->prio ($newprio)	478	=item $oldprio = $coroutine->prio ($newprio)
321		479
322	Sets (or gets, if the argument is missing) the priority of the	480	Sets (or gets, if the argument is missing) the priority of the
…		…
345	higher values mean lower priority, just as in unix).	503	higher values mean lower priority, just as in unix).
346		504
347	=item $olddesc = $coroutine->desc ($newdesc)	505	=item $olddesc = $coroutine->desc ($newdesc)
348		506
349	Sets (or gets in case the argument is missing) the description for this	507	Sets (or gets in case the argument is missing) the description for this
350	coroutine. This is just a free-form string you can associate with a coroutine.	508	coroutine. This is just a free-form string you can associate with a
		509	coroutine.
		510
		511	This method simply sets the C<< $coroutine->{desc} >> member to the given
		512	string. You can modify this member directly if you wish.
351		513
352	=cut	514	=cut
353		515
354	sub desc {	516	sub desc {
355	my $old = $_[0]{desc};	517	my $old = $_[0]{desc};
…		…
364	=over 4	526	=over 4
365		527
366	=item Coro::nready	528	=item Coro::nready
367		529
368	Returns the number of coroutines that are currently in the ready state,	530	Returns the number of coroutines that are currently in the ready state,
369	i.e. that can be swicthed to. The value C<0> means that the only runnable	531	i.e. that can be switched to by calling C<schedule> directory or
		532	indirectly. The value C<0> means that the only runnable coroutine is the
370	coroutine is the currently running one, so C<cede> would have no effect,	533	currently running one, so C<cede> would have no effect, and C<schedule>
371	and C<schedule> would cause a deadlock unless there is an idle handler	534	would cause a deadlock unless there is an idle handler that wakes up some
372	that wakes up some coroutines.	535	coroutines.
		536
		537	=item my $guard = Coro::guard { ... }
		538
		539	This creates and returns a guard object. Nothing happens until the object
		540	gets destroyed, in which case the codeblock given as argument will be
		541	executed. This is useful to free locks or other resources in case of a
		542	runtime error or when the coroutine gets canceled, as in both cases the
		543	guard block will be executed. The guard object supports only one method,
		544	C<< ->cancel >>, which will keep the codeblock from being executed.
		545
		546	Example: set some flag and clear it again when the coroutine gets canceled
		547	or the function returns:
		548
		549	sub do_something {
		550	my $guard = Coro::guard { $busy = 0 };
		551	$busy = 1;
		552
		553	# do something that requires $busy to be true
		554	}
		555
		556	=cut
		557
		558	sub guard(&) {
		559	bless \(my $cb = $_[0]), "Coro::guard"
		560	}
		561
		562	sub Coro::guard::cancel {
		563	${$_[0]} = sub { };
		564	}
		565
		566	sub Coro::guard::DESTROY {
		567	${$_[0]}->();
		568	}
		569
373		570
374	=item unblock_sub { ... }	571	=item unblock_sub { ... }
375		572
376	This utility function takes a BLOCK or code reference and "unblocks" it,	573	This utility function takes a BLOCK or code reference and "unblocks" it,
377	returning the new coderef. This means that the new coderef will return	574	returning a new coderef. Unblocking means that calling the new coderef
378	immediately without blocking, returning nothing, while the original code	575	will return immediately without blocking, returning nothing, while the
379	ref will be called (with parameters) from within its own coroutine.	576	original code ref will be called (with parameters) from within another
		577	coroutine.
380		578
381	The reason this fucntion exists is that many event libraries (such as the	579	The reason this function exists is that many event libraries (such as the
382	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	580	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
383	of thread-safety). This means you must not block within event callbacks,	581	of thread-safety). This means you must not block within event callbacks,
384	otherwise you might suffer from crashes or worse.	582	otherwise you might suffer from crashes or worse. The only event library
		583	currently known that is safe to use without C<unblock_sub> is L<EV>.
385		584
386	This function allows your callbacks to block by executing them in another	585	This function allows your callbacks to block by executing them in another
387	coroutine where it is safe to block. One example where blocking is handy	586	coroutine where it is safe to block. One example where blocking is handy
388	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	587	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
389	disk.	588	disk, for example.
390		589
391	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	590	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
392	creating event callbacks that want to block.	591	creating event callbacks that want to block.
393		592
394	=cut	593	If your handler does not plan to block (e.g. simply sends a message to
		594	another coroutine, or puts some other coroutine into the ready queue),
		595	there is no reason to use C<unblock_sub>.
395		596
396	our @unblock_pool;	597	Note that you also need to use C<unblock_sub> for any other callbacks that
		598	are indirectly executed by any C-based event loop. For example, when you
		599	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		600	provides callbacks that are the result of some event callback, then you
		601	must not block either, or use C<unblock_sub>.
		602
		603	=cut
		604
397	our @unblock_queue;	605	our @unblock_queue;
398	our $UNBLOCK_POOL_SIZE = 2;
399		606
400	sub unblock_handler_ {	607	# we create a special coro because we want to cede,
401	while () {	608	# to reduce pressure on the coro pool (because most callbacks
402	my ($cb, @arg) = @{ delete $Coro::current->{arg} };	609	# return immediately and can be reused) and because we cannot cede
403	$cb->(@arg);	610	# inside an event callback.
404
405	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
406	push @unblock_pool, $Coro::current;
407	schedule;
408	}
409	}
410
411	our $unblock_scheduler = async {	611	our $unblock_scheduler = new Coro sub {
412	while () {	612	while () {
413	while (my $cb = pop @unblock_queue) {	613	while (my $cb = pop @unblock_queue) {
414	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);	614	&async_pool (@$cb);
415	$handler->{arg} = $cb;	615
416	$handler->ready;	616	# for short-lived callbacks, this reduces pressure on the coro pool
		617	# as the chance is very high that the async_poll coro will be back
		618	# in the idle state when cede returns
417	cede;	619	cede;
418	}	620	}
419		621	schedule; # sleep well
420	schedule;
421	}	622	}
422	};	623	};
		624	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
423		625
424	sub unblock_sub(&) {	626	sub unblock_sub(&) {
425	my $cb = shift;	627	my $cb = shift;
426		628
427	sub {	629	sub {
428	push @unblock_queue, [$cb, @_];	630	unshift @unblock_queue, [$cb, @_];
429	$unblock_scheduler->ready;	631	$unblock_scheduler->ready;
430	}	632	}
431	}	633	}
432		634
		635	=item $cb = Coro::rouse_cb
		636
		637	Create and return a "rouse callback". That's a code reference that, when
		638	called, will save its arguments and notify the owner coroutine of the
		639	callback.
		640
		641	See the next function.
		642
		643	=item @args = Coro::rouse_wait [$cb]
		644
		645	Wait for the specified rouse callback (or the last one tht was created in
		646	this coroutine).
		647
		648	As soon as the callback is invoked (or when the calback was invoked before
		649	C<rouse_wait>), it will return a copy of the arguments originally passed
		650	to the rouse callback.
		651
		652	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		653
433	=back	654	=back
434		655
435	=cut	656	=cut
436		657
437	1;	658	1;
438		659
		660	=head1 HOW TO WAIT FOR A CALLBACK
		661
		662	It is very common for a coroutine to wait for some callback to be
		663	called. This occurs naturally when you use coroutines in an otherwise
		664	event-based program, or when you use event-based libraries.
		665
		666	These typically register a callback for some event, and call that callback
		667	when the event occured. In a coroutine, however, you typically want to
		668	just wait for the event, simplyifying things.
		669
		670	For example C<< AnyEvent->child >> registers a callback to be called when
		671	a specific child has exited:
		672
		673	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		674
		675	But from withina coroutine, you often just want to write this:
		676
		677	my $status = wait_for_child $pid;
		678
		679	Coro offers two functions specifically designed to make this easy,
		680	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		681
		682	The first function, C<rouse_cb>, generates and returns a callback that,
		683	when invoked, will save it's arguments and notify the coroutine that
		684	created the callback.
		685
		686	The second function, C<rouse_wait>, waits for the callback to be called
		687	(by calling C<schedule> to go to sleep) and returns the arguments
		688	originally passed to the callback.
		689
		690	Using these functions, it becomes easy to write the C<wait_for_child>
		691	function mentioned above:
		692
		693	sub wait_for_child($) {
		694	my ($pid) = @_;
		695
		696	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		697
		698	my ($rpid, $rstatus) = Coro::rouse_wait;
		699	$rstatus
		700	}
		701
		702	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		703	you can roll your own, using C<schedule>:
		704
		705	sub wait_for_child($) {
		706	my ($pid) = @_;
		707
		708	# store the current coroutine in $current,
		709	# and provide result variables for the closure passed to ->child
		710	my $current = $Coro::current;
		711	my ($done, $rstatus);
		712
		713	# pass a closure to ->child
		714	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		715	$rstatus = $_[1]; # remember rstatus
		716	$done = 1; # mark $rstatus as valud
		717	});
		718
		719	# wait until the closure has been called
		720	schedule while !$done;
		721
		722	$rstatus
		723	}
		724
		725
439	=head1 BUGS/LIMITATIONS	726	=head1 BUGS/LIMITATIONS
440		727
441	- you must make very sure that no coro is still active on global	728	=over 4
442	destruction. very bad things might happen otherwise (usually segfaults).
443		729
		730	=item fork with pthread backend
		731
		732	When Coro is compiled using the pthread backend (which isn't recommended
		733	but required on many BSDs as their libcs are completely broken), then
		734	coroutines will not survive a fork. There is no known workaround except to
		735	fix your libc and use a saner backend.
		736
		737	=item perl process emulation ("threads")
		738
444	- this module is not thread-safe. You should only ever use this module	739	This module is not perl-pseudo-thread-safe. You should only ever use this
445	from the same thread (this requirement might be losened in the future	740	module from the same thread (this requirement might be removed in the
446	to allow per-thread schedulers, but Coro::State does not yet allow	741	future to allow per-thread schedulers, but Coro::State does not yet allow
447	this).	742	this). I recommend disabling thread support and using processes, as having
		743	the windows process emulation enabled under unix roughly halves perl
		744	performance, even when not used.
		745
		746	=item coroutine switching not signal safe
		747
		748	You must not switch to another coroutine from within a signal handler
		749	(only relevant with %SIG - most event libraries provide safe signals).
		750
		751	That means you I<MUST NOT> call any function that might "block" the
		752	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		753	anything that calls those. Everything else, including calling C<ready>,
		754	works.
		755
		756	=back
		757
448		758
449	=head1 SEE ALSO	759	=head1 SEE ALSO
450		760
		761	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		762
		763	Debugging: L<Coro::Debug>.
		764
451	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	765	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
452		766
453	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	767	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
454		768
455	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	769	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
456		770
457	Embedding: L<Coro:MakeMaker>	771	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		772
		773	XS API: L<Coro::MakeMaker>.
		774
		775	Low level Configuration, Coroutine Environment: L<Coro::State>.
458		776
459	=head1 AUTHOR	777	=head1 AUTHOR
460		778
461	Marc Lehmann <schmorp@schmorp.de>	779	Marc Lehmann <schmorp@schmorp.de>
462	http://home.schmorp.de/	780	http://home.schmorp.de/

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Comparing Coro/Coro.pm (file contents): Revision 1.100 by root, Tue Dec 12 13:56:45 2006 UTC vs. Revision 1.229 by root, Thu Nov 20 06:32:55 2008 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.100 by root, Tue Dec 12 13:56:45 2006 UTC vs.
Revision 1.229 by root, Thu Nov 20 06:32:55 2008 UTC