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

Comparing Coro/Coro.pm (file contents):
Revision 1.108 by root, Fri Jan 5 20:00:49 2007 UTC vs.
Revision 1.228 by root, Thu Nov 20 03:14:49 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 = '3.3';	72	our $VERSION = 5.0;
56		73
57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
58	our %EXPORT_TAGS = (	75	our %EXPORT_TAGS = (
59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60	);	77	);
61	our @EXPORT_OK = (@{$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;
…		…
149	# free coroutine data and mark as destructed	143	# free coroutine data and mark as destructed
150	$self->_destroy	144	$self->_destroy
151	or return;	145	or return;
152		146
153	# call all destruction callbacks	147	# call all destruction callbacks
154	$_->(@{$self->{status}})	148	$_->(@{$self->{_status}})
155	for @{(delete $self->{destroy_cb}) \|\| []};	149	for @{ delete $self->{_on_destroy} \|\| [] };
156	}	150	}
157		151
158	# this coroutine is necessary because a coroutine	152	# this coroutine is necessary because a coroutine
159	# cannot destroy itself.	153	# cannot destroy itself.
160	my @destroy;	154	our @destroy;
161	my $manager;	155	our $manager;
162		156
163	$manager = new Coro sub {	157	$manager = new Coro sub {
164	while () {	158	while () {
165	(shift @destroy)->_cancel	159	(shift @destroy)->_cancel
166	while @destroy;	160	while @destroy;
167		161
168	&schedule;	162	&schedule;
169	}	163	}
170	};	164	};
171		165	$manager->{desc} = "[coro manager]";
172	$manager->prio (PRIO_MAX);	166	$manager->prio (PRIO_MAX);
173		167
174	# static methods. not really.
175
176	=back	168	=back
177		169
178	=head2 STATIC METHODS	170	=head2 SIMPLE COROUTINE CREATION
179
180	Static methods are actually functions that operate on the current coroutine only.
181		171
182	=over 4	172	=over 4
183		173
184	=item async { ... } [@args...]	174	=item async { ... } [@args...]
185		175
186	Create a new asynchronous coroutine and return it's coroutine object	176	Create a new coroutine and return it's coroutine object (usually
187	(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
188	terminated.	182	terminated.
189		183
190	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.
191		185
192	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
193	program.	187	environment in which coroutines are executed.
194		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
195	# create a new coroutine that just prints its arguments	196	Example: Create a new coroutine that just prints its arguments.
		197
196	async {	198	async {
197	print "@_\n";	199	print "@_\n";
198	} 1,2,3,4;	200	} 1,2,3,4;
199		201
200	=cut	202	=cut
…		…
206	}	208	}
207		209
208	=item async_pool { ... } [@args...]	210	=item async_pool { ... } [@args...]
209		211
210	Similar to C<async>, but uses a coroutine pool, so you should not call	212	Similar to C<async>, but uses a coroutine pool, so you should not call
211	terminate or join (although you are allowed to), and you get a coroutine	213	terminate or join on it (although you are allowed to), and you get a
212	that might have executed other code already (which can be good or bad :).	214	coroutine that might have executed other code already (which can be good
		215	or bad :).
213		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
214	Also, the block is executed in an C<eval> context and a warning will be	221	The code block is executed in an C<eval> context and a warning will be
215	issued in case of an exception instead of terminating the program, as	222	issued in case of an exception instead of terminating the program, as
216	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>	223	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
217	will not work in the expected way, unless you call terminate or cancel,	224	will not work in the expected way, unless you call terminate or cancel,
218	which somehow defeats the purpose of pooling.	225	which somehow defeats the purpose of pooling (but is fine in the
		226	exceptional case).
219		227
220	The priority will be reset to C<0> after each job, otherwise the coroutine	228	The priority will be reset to C<0> after each run, tracing will be
221	will be re-used "as-is".	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 $/ >>.
222		234
223	The pool size is limited to 8 idle coroutines (this can be adjusted by	235	The idle pool size is limited to C<8> idle coroutines (this can be
224	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as	236	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
225	required.	237	coros as required.
226		238
227	If you are concerned about pooled coroutines growing a lot because a	239	If you are concerned about pooled coroutines growing a lot because a
228	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {	240	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
229	terminate }> once per second or so to slowly replenish the 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.
230		244
231	=cut	245	=cut
232		246
233	our $POOL_SIZE = 8;	247	our $POOL_SIZE = 8;
		248	our $POOL_RSS = 16 * 1024;
234	our @pool;	249	our @async_pool;
235		250
236	sub pool_handler {	251	sub pool_handler {
237	while () {	252	while () {
238	my ($cb, @arg) = @{ delete $current->{_invoke} };
239
240	eval {	253	eval {
241	$cb->(@arg);	254	&{&_pool_handler} while 1;
242	};	255	};
		256
243	warn $@ if $@;	257	warn $@ if $@;
244
245	last if @pool >= $POOL_SIZE;
246	push @pool, $current;
247
248	$current->prio (0);
249	schedule;
250	}	258	}
251	}	259	}
252		260
253	sub async_pool(&@) {	261	=back
254	# this is also inlined into the unlock_scheduler
255	my $coro = (pop @pool or new Coro \&pool_handler);
256		262
257	$coro->{_invoke} = [@_];	263	=head2 STATIC METHODS
258	$coro->ready;
259		264
260	$coro	265	Static methods are actually functions that operate on the current coroutine.
261	}	266
		267	=over 4
262		268
263	=item schedule	269	=item schedule
264		270
265	Calls the scheduler. Please note that the current coroutine will not be put	271	Calls the scheduler. The scheduler will find the next coroutine that is
		272	to be run from the ready queue and switches to it. The next coroutine
		273	to be run is simply the one with the highest priority that is longest
		274	in its ready queue. If there is no coroutine ready, it will clal the
		275	C<$Coro::idle> hook.
		276
		277	Please note that the current coroutine will I<not> be put into the ready
266	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
267	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 >>,
268	ready.	280	thus waking you up.
269		281
270	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.
271		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";
272	{	335	}
273	# 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 $coroutine->throw ([$scalar])
		397
		398	If C<$throw> is specified and defined, it will be thrown as an exception
		399	inside the coroutine at the next convenient point in time. Otherwise
		400	clears the exception object.
		401
		402	Coro will check for the exception each time a schedule-like-function
		403	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		404	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		405	detect this case and return early in case an exception is pending.
		406
		407	The exception object will be thrown "as is" with the specified scalar in
		408	C<$@>, i.e. if it is a string, no line number or newline will be appended
		409	(unlike with C<die>).
		410
		411	This can be used as a softer means than C<cancel> to ask a coroutine to
		412	end itself, although there is no guarantee that the exception will lead to
		413	termination, and if the exception isn't caught it might well end the whole
		414	program.
		415
		416	You might also think of C<throw> as being the moral equivalent of
		417	C<kill>ing a coroutine with a signal (in this case, a scalar).
		418
		419	=item $coroutine->join
		420
		421	Wait until the coroutine terminates and return any values given to the
		422	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		423	from multiple coroutines, and all will be resumed and given the status
		424	return once the C<$coroutine> terminates.
		425
		426	=cut
		427
		428	sub join {
		429	my $self = shift;
		430
		431	unless ($self->{_status}) {
274	my $current = $Coro::current;	432	my $current = $current;
275		433
276	# register a hypothetical event handler	434	push @{$self->{_on_destroy}}, sub {
277	on_event_invoke sub {
278	# wake up sleeping coroutine
279	$current->ready;	435	$current->ready;
280	undef $current;	436	undef $current;
281	};	437	};
282		438
283	# call schedule until event occured.
284	# in case we are woken up for other reasons
285	# (current still defined), loop.
286	Coro::schedule while $current;
287	}
288
289	=item cede
290
291	"Cede" to other coroutines. This function puts the current coroutine into the
292	ready queue and calls C<schedule>, which has the effect of giving up the
293	current "timeslice" to other coroutines of the same or higher priority.
294
295	Returns true if at least one coroutine switch has happened.
296
297	=item Coro::cede_notself
298
299	Works like cede, but is not exported by default and will cede to any
300	coroutine, regardless of priority, once.
301
302	Returns true if at least one coroutine switch has happened.
303
304	=item terminate [arg...]
305
306	Terminates the current coroutine with the given status values (see L<cancel>).
307
308	=cut
309
310	sub terminate {
311	$current->cancel (@_);
312	}
313
314	=back
315
316	# dynamic methods
317
318	=head2 COROUTINE METHODS
319
320	These are the methods you can call on coroutine objects.
321
322	=over 4
323
324	=item new Coro \&sub [, @args...]
325
326	Create a new coroutine and return it. When the sub returns the coroutine
327	automatically terminates as if C<terminate> with the returned values were
328	called. To make the coroutine run you must first put it into the ready queue
329	by calling the ready method.
330
331	Calling C<exit> in a coroutine will not work correctly, so do not do that.
332
333	=cut
334
335	sub _run_coro {
336	terminate &{+shift};
337	}
338
339	sub new {
340	my $class = shift;
341
342	$class->SUPER::new (\&_run_coro, @_)
343	}
344
345	=item $success = $coroutine->ready
346
347	Put the given coroutine into the ready queue (according to it's priority)
348	and return true. If the coroutine is already in the ready queue, do nothing
349	and return false.
350
351	=item $is_ready = $coroutine->is_ready
352
353	Return wether the coroutine is currently the ready queue or not,
354
355	=item $coroutine->cancel (arg...)
356
357	Terminates the given coroutine and makes it return the given arguments as
358	status (default: the empty list). Never returns if the coroutine is the
359	current coroutine.
360
361	=cut
362
363	sub cancel {
364	my $self = shift;
365	$self->{status} = [@_];
366
367	if ($current == $self) {
368	push @destroy, $self;
369	$manager->ready;
370	&schedule while 1;
371	} else {
372	$self->_cancel;
373	}
374	}
375
376	=item $coroutine->join
377
378	Wait until the coroutine terminates and return any values given to the
379	C<terminate> or C<cancel> functions. C<join> can be called multiple times
380	from multiple coroutine.
381
382	=cut
383
384	sub join {
385	my $self = shift;
386
387	unless ($self->{status}) {
388	my $current = $current;
389
390	push @{$self->{destroy_cb}}, sub {
391	$current->ready;
392	undef $current;
393	};
394
395	&schedule while $current;	439	&schedule while $current;
396	}	440	}
397		441
398	wantarray ? @{$self->{status}} : $self->{status}[0];	442	wantarray ? @{$self->{_status}} : $self->{_status}[0];
399	}	443	}
400		444
401	=item $coroutine->on_destroy (\&cb)	445	=item $coroutine->on_destroy (\&cb)
402		446
403	Registers a callback that is called when this coroutine gets destroyed,	447	Registers a callback that is called when this coroutine gets destroyed,
404	but before it is joined. The callback gets passed the terminate arguments,	448	but before it is joined. The callback gets passed the terminate arguments,
405	if any.	449	if any, and I<must not> die, under any circumstances.
406		450
407	=cut	451	=cut
408		452
409	sub on_destroy {	453	sub on_destroy {
410	my ($self, $cb) = @_;	454	my ($self, $cb) = @_;
411		455
412	push @{ $self->{destroy_cb} }, $cb;	456	push @{ $self->{_on_destroy} }, $cb;
413	}	457	}
414		458
415	=item $oldprio = $coroutine->prio ($newprio)	459	=item $oldprio = $coroutine->prio ($newprio)
416		460
417	Sets (or gets, if the argument is missing) the priority of the	461	Sets (or gets, if the argument is missing) the priority of the
…		…
440	higher values mean lower priority, just as in unix).	484	higher values mean lower priority, just as in unix).
441		485
442	=item $olddesc = $coroutine->desc ($newdesc)	486	=item $olddesc = $coroutine->desc ($newdesc)
443		487
444	Sets (or gets in case the argument is missing) the description for this	488	Sets (or gets in case the argument is missing) the description for this
445	coroutine. This is just a free-form string you can associate with a coroutine.	489	coroutine. This is just a free-form string you can associate with a
		490	coroutine.
		491
		492	This method simply sets the C<< $coroutine->{desc} >> member to the given
		493	string. You can modify this member directly if you wish.
446		494
447	=cut	495	=cut
448		496
449	sub desc {	497	sub desc {
450	my $old = $_[0]{desc};	498	my $old = $_[0]{desc};
…		…
459	=over 4	507	=over 4
460		508
461	=item Coro::nready	509	=item Coro::nready
462		510
463	Returns the number of coroutines that are currently in the ready state,	511	Returns the number of coroutines that are currently in the ready state,
464	i.e. that can be swicthed to. The value C<0> means that the only runnable	512	i.e. that can be switched to by calling C<schedule> directory or
		513	indirectly. The value C<0> means that the only runnable coroutine is the
465	coroutine is the currently running one, so C<cede> would have no effect,	514	currently running one, so C<cede> would have no effect, and C<schedule>
466	and C<schedule> would cause a deadlock unless there is an idle handler	515	would cause a deadlock unless there is an idle handler that wakes up some
467	that wakes up some coroutines.	516	coroutines.
468		517
469	=item my $guard = Coro::guard { ... }	518	=item my $guard = Coro::guard { ... }
470		519
471	This creates and returns a guard object. Nothing happens until the objetc	520	This creates and returns a guard object. Nothing happens until the object
472	gets destroyed, in which case the codeblock given as argument will be	521	gets destroyed, in which case the codeblock given as argument will be
473	executed. This is useful to free locks or other resources in case of a	522	executed. This is useful to free locks or other resources in case of a
474	runtime error or when the coroutine gets canceled, as in both cases the	523	runtime error or when the coroutine gets canceled, as in both cases the
475	guard block will be executed. The guard object supports only one method,	524	guard block will be executed. The guard object supports only one method,
476	C<< ->cancel >>, which will keep the codeblock from being executed.	525	C<< ->cancel >>, which will keep the codeblock from being executed.
…		…
501		550
502		551
503	=item unblock_sub { ... }	552	=item unblock_sub { ... }
504		553
505	This utility function takes a BLOCK or code reference and "unblocks" it,	554	This utility function takes a BLOCK or code reference and "unblocks" it,
506	returning the new coderef. This means that the new coderef will return	555	returning a new coderef. Unblocking means that calling the new coderef
507	immediately without blocking, returning nothing, while the original code	556	will return immediately without blocking, returning nothing, while the
508	ref will be called (with parameters) from within its own coroutine.	557	original code ref will be called (with parameters) from within another
		558	coroutine.
509		559
510	The reason this fucntion exists is that many event libraries (such as the	560	The reason this function exists is that many event libraries (such as the
511	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	561	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
512	of thread-safety). This means you must not block within event callbacks,	562	of thread-safety). This means you must not block within event callbacks,
513	otherwise you might suffer from crashes or worse.	563	otherwise you might suffer from crashes or worse. The only event library
		564	currently known that is safe to use without C<unblock_sub> is L<EV>.
514		565
515	This function allows your callbacks to block by executing them in another	566	This function allows your callbacks to block by executing them in another
516	coroutine where it is safe to block. One example where blocking is handy	567	coroutine where it is safe to block. One example where blocking is handy
517	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	568	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
518	disk.	569	disk, for example.
519		570
520	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	571	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
521	creating event callbacks that want to block.	572	creating event callbacks that want to block.
		573
		574	If your handler does not plan to block (e.g. simply sends a message to
		575	another coroutine, or puts some other coroutine into the ready queue),
		576	there is no reason to use C<unblock_sub>.
		577
		578	Note that you also need to use C<unblock_sub> for any other callbacks that
		579	are indirectly executed by any C-based event loop. For example, when you
		580	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		581	provides callbacks that are the result of some event callback, then you
		582	must not block either, or use C<unblock_sub>.
522		583
523	=cut	584	=cut
524		585
525	our @unblock_queue;	586	our @unblock_queue;
526		587
527	# we create a special coro because we want to cede,	588	# we create a special coro because we want to cede,
528	# to reduce pressure on the coro pool (because most callbacks	589	# to reduce pressure on the coro pool (because most callbacks
529	# return immediately and can be reused) and because we cannot cede	590	# return immediately and can be reused) and because we cannot cede
530	# inside an event callback.	591	# inside an event callback.
531	our $unblock_scheduler = async {	592	our $unblock_scheduler = new Coro sub {
532	while () {	593	while () {
533	while (my $cb = pop @unblock_queue) {	594	while (my $cb = pop @unblock_queue) {
534	# this is an inlined copy of async_pool	595	&async_pool (@$cb);
535	my $coro = (pop @pool or new Coro \&pool_handler);
536		596
537	$coro->{_invoke} = $cb;
538	$coro->ready;
539	cede; # for short-lived callbacks, this reduces pressure on the coro pool	597	# for short-lived callbacks, this reduces pressure on the coro pool
		598	# as the chance is very high that the async_poll coro will be back
		599	# in the idle state when cede returns
		600	cede;
540	}	601	}
541	schedule; # sleep well	602	schedule; # sleep well
542	}	603	}
543	};	604	};
		605	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
544		606
545	sub unblock_sub(&) {	607	sub unblock_sub(&) {
546	my $cb = shift;	608	my $cb = shift;
547		609
548	sub {	610	sub {
549	unshift @unblock_queue, [$cb, @_];	611	unshift @unblock_queue, [$cb, @_];
550	$unblock_scheduler->ready;	612	$unblock_scheduler->ready;
551	}	613	}
552	}	614	}
553		615
		616	=item $cb = Coro::rouse_cb
		617
		618	Create and return a "rouse callback". That's a code reference that, when
		619	called, will save its arguments and notify the owner coroutine of the
		620	callback.
		621
		622	See the next function.
		623
		624	=item @args = Coro::rouse_wait [$cb]
		625
		626	Wait for the specified rouse callback (or the last one tht was created in
		627	this coroutine).
		628
		629	As soon as the callback is invoked (or when the calback was invoked before
		630	C<rouse_wait>), it will return a copy of the arguments originally passed
		631	to the rouse callback.
		632
		633	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		634
554	=back	635	=back
555		636
556	=cut	637	=cut
557		638
558	1;	639	1;
559		640
		641	=head1 HOW TO WAIT FOR A CALLBACK
		642
		643	It is very common for a coroutine to wait for some callback to be
		644	called. This occurs naturally when you use coroutines in an otherwise
		645	event-based program, or when you use event-based libraries.
		646
		647	These typically register a callback for some event, and call that callback
		648	when the event occured. In a coroutine, however, you typically want to
		649	just wait for the event, simplyifying things.
		650
		651	For example C<< AnyEvent->child >> registers a callback to be called when
		652	a specific child has exited:
		653
		654	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		655
		656	But from withina coroutine, you often just want to write this:
		657
		658	my $status = wait_for_child $pid;
		659
		660	Coro offers two functions specifically designed to make this easy,
		661	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		662
		663	The first function, C<rouse_cb>, generates and returns a callback that,
		664	when invoked, will save it's arguments and notify the coroutine that
		665	created the callback.
		666
		667	The second function, C<rouse_wait>, waits for the callback to be called
		668	(by calling C<schedule> to go to sleep) and returns the arguments
		669	originally passed to the callback.
		670
		671	Using these functions, it becomes easy to write the C<wait_for_child>
		672	function mentioned above:
		673
		674	sub wait_for_child($) {
		675	my ($pid) = @_;
		676
		677	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		678
		679	my ($rpid, $rstatus) = Coro::rouse_wait;
		680	$rstatus
		681	}
		682
		683	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		684	you can roll your own, using C<schedule>:
		685
		686	sub wait_for_child($) {
		687	my ($pid) = @_;
		688
		689	# store the current coroutine in $current,
		690	# and provide result variables for the closure passed to ->child
		691	my $current = $Coro::current;
		692	my ($done, $rstatus);
		693
		694	# pass a closure to ->child
		695	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		696	$rstatus = $_[1]; # remember rstatus
		697	$done = 1; # mark $rstatus as valud
		698	});
		699
		700	# wait until the closure has been called
		701	schedule while !$done;
		702
		703	$rstatus
		704	}
		705
		706
560	=head1 BUGS/LIMITATIONS	707	=head1 BUGS/LIMITATIONS
561		708
562	- you must make very sure that no coro is still active on global	709	=over 4
563	destruction. very bad things might happen otherwise (usually segfaults).
564		710
		711	=item fork with pthread backend
		712
		713	When Coro is compiled using the pthread backend (which isn't recommended
		714	but required on many BSDs as their libcs are completely broken), then
		715	coroutines will not survive a fork. There is no known workaround except to
		716	fix your libc and use a saner backend.
		717
		718	=item perl process emulation ("threads")
		719
565	- this module is not thread-safe. You should only ever use this module	720	This module is not perl-pseudo-thread-safe. You should only ever use this
566	from the same thread (this requirement might be losened in the future	721	module from the same thread (this requirement might be removed in the
567	to allow per-thread schedulers, but Coro::State does not yet allow	722	future to allow per-thread schedulers, but Coro::State does not yet allow
568	this).	723	this). I recommend disabling thread support and using processes, as having
		724	the windows process emulation enabled under unix roughly halves perl
		725	performance, even when not used.
		726
		727	=item coroutine switching not signal safe
		728
		729	You must not switch to another coroutine from within a signal handler
		730	(only relevant with %SIG - most event libraries provide safe signals).
		731
		732	That means you I<MUST NOT> call any function that might "block" the
		733	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		734	anything that calls those. Everything else, including calling C<ready>,
		735	works.
		736
		737	=back
		738
569		739
570	=head1 SEE ALSO	740	=head1 SEE ALSO
571		741
		742	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		743
		744	Debugging: L<Coro::Debug>.
		745
572	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	746	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
573		747
574	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	748	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
575		749
576	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	750	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
577		751
578	Embedding: L<Coro:MakeMaker>	752	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		753
		754	XS API: L<Coro::MakeMaker>.
		755
		756	Low level Configuration, Coroutine Environment: L<Coro::State>.
579		757
580	=head1 AUTHOR	758	=head1 AUTHOR
581		759
582	Marc Lehmann <schmorp@schmorp.de>	760	Marc Lehmann <schmorp@schmorp.de>
583	http://home.schmorp.de/	761	http://home.schmorp.de/

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Revision 1.228 by root, Thu Nov 20 03:14:49 2008 UTC