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Revision 1.179 by root, Sat Apr 19 19:06:02 2008 UTC vs.
Revision 1.247 by root, Mon Dec 15 02:07:11 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - coroutine process abstraction	3	Coro - the only real threads in perl
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use Coro;	7	use Coro;
8		8
16	cede; # yield to coroutine	16	cede; # yield to coroutine
17	print "3\n";	17	print "3\n";
18	cede; # and again	18	cede; # and again
19		19
20	# use locking	20	# use locking
		21	use Coro::Semaphore;
21	my $lock = new Coro::Semaphore;	22	my $lock = new Coro::Semaphore;
22	my $locked;	23	my $locked;
23		24
24	$lock->down;	25	$lock->down;
25	$locked = 1;	26	$locked = 1;
26	$lock->up;	27	$lock->up;
27		28
28	=head1 DESCRIPTION	29	=head1 DESCRIPTION
29		30
30	This module collection manages coroutines. Coroutines are similar	31	For a tutorial-style introduction, please read the L<Coro::Intro>
31	to threads but don't run in parallel at the same time even on SMP	32	manpage. This manpage mainly contains reference information.
32	machines. The specific flavor of coroutine used in this module also
33	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 than threads programming.
37		33
38	(Perl, however, does not natively support real threads but instead does a	34	This module collection manages continuations in general, most often
39	very slow and memory-intensive emulation of processes using threads. This	35	in the form of cooperative threads (also called coroutines in the
40	is a performance win on Windows machines, and a loss everywhere else).	36	documentation). They are similar to kernel threads but don't (in general)
		37	run in parallel at the same time even on SMP machines. The specific flavor
		38	of thread offered by this module also guarantees you that it will not
		39	switch between threads unless necessary, at easily-identified points in
		40	your program, so locking and parallel access are rarely an issue, making
		41	thread programming much safer and easier than using other thread models.
41		42
		43	Unlike the so-called "Perl threads" (which are not actually real threads
		44	but only the windows process emulation ported to unix), Coro provides a
		45	full shared address space, which makes communication between threads
		46	very easy. And threads are fast, too: disabling the Windows process
		47	emulation code in your perl and using Coro can easily result in a two to
		48	four times speed increase for your programs.
		49
		50	Coro achieves that by supporting multiple running interpreters that share
		51	data, which is especially useful to code pseudo-parallel processes and
		52	for event-based programming, such as multiple HTTP-GET requests running
		53	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		54	into an event-based environment.
		55
42	In this module, coroutines are defined as "callchain + lexical variables +	56	In this module, a thread is defined as "callchain + lexical variables +
43	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	57	@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,
44	its own set of lexicals and its own set of perls most important global	58	its own set of lexicals and its own set of perls most important global
45	variables (see L<Coro::State> for more configuration).	59	variables (see L<Coro::State> for more configuration and background info).
		60
		61	See also the C<SEE ALSO> section at the end of this document - the Coro
		62	module family is quite large.
46		63
47	=cut	64	=cut
48		65
49	package Coro;	66	package Coro;
50		67
51	use strict;	68	use strict qw(vars subs);
52	no warnings "uninitialized";	69	no warnings "uninitialized";
		70
		71	use Guard ();
53		72
54	use Coro::State;	73	use Coro::State;
55		74
56	use base qw(Coro::State Exporter);	75	use base qw(Coro::State Exporter);
57		76
58	our $idle; # idle handler	77	our $idle; # idle handler
59	our $main; # main coroutine	78	our $main; # main coroutine
60	our $current; # current coroutine	79	our $current; # current coroutine
61		80
62	our $VERSION = '4.51';	81	our $VERSION = 5.13;
63		82
64	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	83	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
65	our %EXPORT_TAGS = (	84	our %EXPORT_TAGS = (
66	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	85	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
67	);	86	);
68	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	87	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
69		88
		89	=head1 GLOBAL VARIABLES
		90
70	=over 4	91	=over 4
71		92
72	=item $main	93	=item $Coro::main
73		94
74	This coroutine represents the main program.	95	This variable stores the coroutine object that represents the main
		96	program. While you cna C<ready> it and do most other things you can do to
		97	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		98	whether you are running in the main program or not.
75		99
76	=cut	100	=cut
77		101
78	$main = new Coro;	102	# $main is now being initialised by Coro::State
79		103
80	=item $current (or as function: current)	104	=item $Coro::current
81		105
82	The current coroutine (the last coroutine switched to). The initial value	106	The coroutine object representing the current coroutine (the last
		107	coroutine that the Coro scheduler switched to). The initial value is
83	is C<$main> (of course).	108	C<$Coro::main> (of course).
84		109
85	This variable is B<strictly> I<read-only>. It is provided for performance	110	This variable is B<strictly> I<read-only>. You can take copies of the
86	reasons. If performance is not essential you are encouraged to use the	111	value stored in it and use it as any other coroutine object, but you must
87	C<Coro::current> function instead.	112	not otherwise modify the variable itself.
88		113
89	=cut	114	=cut
90		115
91	$main->{desc} = "[main::]";
92
93	# maybe some other module used Coro::Specific before...
94	$main->{_specific} = $current->{_specific}
95	if $current;
96
97	_set_current $main;
98
99	sub current() { $current }	116	sub current() { $current } # [DEPRECATED]
100		117
101	=item $idle	118	=item $Coro::idle
102		119
		120	This variable is mainly useful to integrate Coro into event loops. It is
		121	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		122	pretty low-level functionality.
		123
		124	This variable stores either a coroutine or a callback.
		125
103	A callback that is called whenever the scheduler finds no ready coroutines	126	If it is a callback, the it is called whenever the scheduler finds no
104	to run. The default implementation prints "FATAL: deadlock detected" and	127	ready coroutines to run. The default implementation prints "FATAL:
105	exits, because the program has no other way to continue.	128	deadlock detected" and exits, because the program has no other way to
		129	continue.
106		130
		131	If it is a coroutine object, then this object will be readied (without
		132	invoking any ready hooks, however) when the scheduler finds no other ready
		133	coroutines to run.
		134
107	This hook is overwritten by modules such as C<Coro::Timer> and	135	This hook is overwritten by modules such as C<Coro::EV> and
108	C<Coro::Event> to wait on an external event that hopefully wake up a	136	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
109	coroutine so the scheduler can run it.	137	coroutine so the scheduler can run it.
		138
		139	Note that the callback I<must not>, under any circumstances, block
		140	the current coroutine. Normally, this is achieved by having an "idle
		141	coroutine" that calls the event loop and then blocks again, and then
		142	readying that coroutine in the idle handler, or by simply placing the idle
		143	coroutine in this variable.
		144
		145	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		146	technique.
110		147
111	Please note that if your callback recursively invokes perl (e.g. for event	148	Please note that if your callback recursively invokes perl (e.g. for event
112	handlers), then it must be prepared to be called recursively itself.	149	handlers), then it must be prepared to be called recursively itself.
113		150
114	=cut	151	=cut
…		…
116	$idle = sub {	153	$idle = sub {
117	require Carp;	154	require Carp;
118	Carp::croak ("FATAL: deadlock detected");	155	Carp::croak ("FATAL: deadlock detected");
119	};	156	};
120		157
121	sub _cancel {
122	my ($self) = @_;
123
124	# free coroutine data and mark as destructed
125	$self->_destroy
126	or return;
127
128	# call all destruction callbacks
129	$_->(@{$self->{_status}})
130	for @{(delete $self->{_on_destroy}) \|\| []};
131	}
132
133	# this coroutine is necessary because a coroutine	158	# this coroutine is necessary because a coroutine
134	# cannot destroy itself.	159	# cannot destroy itself.
135	my @destroy;	160	our @destroy;
136	my $manager;	161	our $manager;
137		162
138	$manager = new Coro sub {	163	$manager = new Coro sub {
139	while () {	164	while () {
140	(shift @destroy)->_cancel	165	Coro::_cancel shift @destroy
141	while @destroy;	166	while @destroy;
142		167
143	&schedule;	168	&schedule;
144	}	169	}
145	};	170	};
146	$manager->desc ("[coro manager]");	171	$manager->{desc} = "[coro manager]";
147	$manager->prio (PRIO_MAX);	172	$manager->prio (PRIO_MAX);
148		173
149	=back	174	=back
150		175
151	=head2 STATIC METHODS	176	=head1 SIMPLE COROUTINE CREATION
152
153	Static methods are actually functions that operate on the current coroutine only.
154		177
155	=over 4	178	=over 4
156		179
157	=item async { ... } [@args...]	180	=item async { ... } [@args...]
158		181
159	Create a new asynchronous coroutine and return it's coroutine object	182	Create a new coroutine and return its coroutine object (usually
160	(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
161	terminated.	188	terminated.
162		189
		190	The remaining arguments are passed as arguments to the closure.
		191
163	See the C<Coro::State::new> constructor for info about the coroutine	192	See the C<Coro::State::new> constructor for info about the coroutine
164	environment in which coroutines run.	193	environment in which coroutines are executed.
165		194
166	Calling C<exit> in a coroutine will do the same as calling exit outside	195	Calling C<exit> in a coroutine will do the same as calling exit outside
167	the coroutine. Likewise, when the coroutine dies, the program will exit,	196	the coroutine. Likewise, when the coroutine dies, the program will exit,
168	just as it would in the main program.	197	just as it would in the main program.
169		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
170	# create a new coroutine that just prints its arguments	202	Example: Create a new coroutine that just prints its arguments.
		203
171	async {	204	async {
172	print "@_\n";	205	print "@_\n";
173	} 1,2,3,4;	206	} 1,2,3,4;
174		207
175	=cut	208	=cut
…		…
181	}	214	}
182		215
183	=item async_pool { ... } [@args...]	216	=item async_pool { ... } [@args...]
184		217
185	Similar to C<async>, but uses a coroutine pool, so you should not call	218	Similar to C<async>, but uses a coroutine pool, so you should not call
186	terminate or join (although you are allowed to), and you get a coroutine	219	terminate or join on it (although you are allowed to), and you get a
187	that might have executed other code already (which can be good or bad :).	220	coroutine that might have executed other code already (which can be good
		221	or bad :).
188		222
		223	On the plus side, this function is about twice as fast as creating (and
		224	destroying) a completely new coroutine, so if you need a lot of generic
		225	coroutines in quick successsion, use C<async_pool>, not C<async>.
		226
189	Also, the block is executed in an C<eval> context and a warning will be	227	The code block is executed in an C<eval> context and a warning will be
190	issued in case of an exception instead of terminating the program, as	228	issued in case of an exception instead of terminating the program, as
191	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>	229	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
192	will not work in the expected way, unless you call terminate or cancel,	230	will not work in the expected way, unless you call terminate or cancel,
193	which somehow defeats the purpose of pooling.	231	which somehow defeats the purpose of pooling (but is fine in the
		232	exceptional case).
194		233
195	The priority will be reset to C<0> after each job, tracing will be	234	The priority will be reset to C<0> after each run, tracing will be
196	disabled, the description will be reset and the default output filehandle	235	disabled, the description will be reset and the default output filehandle
197	gets restored, so you can change alkl these. Otherwise the coroutine will	236	gets restored, so you can change all these. Otherwise the coroutine will
198	be re-used "as-is": most notably if you change other per-coroutine global	237	be re-used "as-is": most notably if you change other per-coroutine global
199	stuff such as C<$/> you need to revert that change, which is most simply	238	stuff such as C<$/> you I<must needs> revert that change, which is most
200	done by using local as in C< local $/ >.	239	simply done by using local as in: C<< local $/ >>.
201		240
202	The pool size is limited to 8 idle coroutines (this can be adjusted by	241	The idle pool size is limited to C<8> idle coroutines (this can be
203	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as	242	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
204	required.	243	coros as required.
205		244
206	If you are concerned about pooled coroutines growing a lot because a	245	If you are concerned about pooled coroutines growing a lot because a
207	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool	246	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
208	{ terminate }> once per second or so to slowly replenish the pool. In	247	{ terminate }> once per second or so to slowly replenish the pool. In
209	addition to that, when the stacks used by a handler grows larger than 16kb	248	addition to that, when the stacks used by a handler grows larger than 32kb
210	(adjustable with $Coro::POOL_RSS) it will also exit.	249	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
211		250
212	=cut	251	=cut
213		252
214	our $POOL_SIZE = 8;	253	our $POOL_SIZE = 8;
215	our $POOL_RSS = 16 * 1024;	254	our $POOL_RSS = 32 * 1024;
216	our @async_pool;	255	our @async_pool;
217		256
218	sub pool_handler {	257	sub pool_handler {
219	my $cb;
220
221	while () {	258	while () {
222	eval {	259	eval {
223	while () {	260	&{&_pool_handler} while 1;
224	_pool_1 $cb;
225	&$cb;
226	_pool_2 $cb;
227	&schedule;
228	}
229	};	261	};
230		262
231	last if $@ eq "\3async_pool terminate\2\n";
232	warn $@ if $@;	263	warn $@ if $@;
233	}	264	}
234	}	265	}
235		266
236	sub async_pool(&@) {	267	=back
237	# this is also inlined into the unlock_scheduler
238	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
239		268
240	$coro->{_invoke} = [@_];	269	=head1 STATIC METHODS
241	$coro->ready;
242		270
243	$coro	271	Static methods are actually functions that implicitly operate on the
244	}	272	current coroutine.
		273
		274	=over 4
245		275
246	=item schedule	276	=item schedule
247		277
248	Calls the scheduler. Please note that the current coroutine will not be put	278	Calls the scheduler. The scheduler will find the next coroutine that is
		279	to be run from the ready queue and switches to it. The next coroutine
		280	to be run is simply the one with the highest priority that is longest
		281	in its ready queue. If there is no coroutine ready, it will clal the
		282	C<$Coro::idle> hook.
		283
		284	Please note that the current coroutine will I<not> be put into the ready
249	into the ready queue, so calling this function usually means you will	285	queue, so calling this function usually means you will never be called
250	never be called again unless something else (e.g. an event handler) calls	286	again unless something else (e.g. an event handler) calls C<< ->ready >>,
251	ready.	287	thus waking you up.
252		288
253	The canonical way to wait on external events is this:	289	This makes C<schedule> I<the> generic method to use to block the current
		290	coroutine and wait for events: first you remember the current coroutine in
		291	a variable, then arrange for some callback of yours to call C<< ->ready
		292	>> on that once some event happens, and last you call C<schedule> to put
		293	yourself to sleep. Note that a lot of things can wake your coroutine up,
		294	so you need to check whether the event indeed happened, e.g. by storing the
		295	status in a variable.
254		296
255	{	297	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
256	# remember current coroutine
257	my $current = $Coro::current;
258		298
259	# register a hypothetical event handler	299	=item cede
260	on_event_invoke sub {	300
261	# wake up sleeping coroutine	301	"Cede" to other coroutines. This function puts the current coroutine into
262	$current->ready;	302	the ready queue and calls C<schedule>, which has the effect of giving
263	undef $current;	303	up the current "timeslice" to other coroutines of the same or higher
		304	priority. Once your coroutine gets its turn again it will automatically be
		305	resumed.
		306
		307	This function is often called C<yield> in other languages.
		308
		309	=item Coro::cede_notself
		310
		311	Works like cede, but is not exported by default and will cede to I<any>
		312	coroutine, regardless of priority. This is useful sometimes to ensure
		313	progress is made.
		314
		315	=item terminate [arg...]
		316
		317	Terminates the current coroutine with the given status values (see L<cancel>).
		318
		319	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		320
		321	These function install enter and leave winders in the current scope. The
		322	enter block will be executed when on_enter is called and whenever the
		323	current coroutine is re-entered by the scheduler, while the leave block is
		324	executed whenever the current coroutine is blocked by the scheduler, and
		325	also when the containing scope is exited (by whatever means, be it exit,
		326	die, last etc.).
		327
		328	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		329	BLOCKs>. That means: do not even think about calling C<die> without an
		330	eval, and do not even think of entering the scheduler in any way.
		331
		332	Since both BLOCKs are tied to the current scope, they will automatically
		333	be removed when the current scope exits.
		334
		335	These functions implement the same concept as C<dynamic-wind> in scheme
		336	does, and are useful when you want to localise some resource to a specific
		337	coroutine.
		338
		339	They slow down coroutine switching considerably for coroutines that use
		340	them (But coroutine switching is still reasonably fast if the handlers are
		341	fast).
		342
		343	These functions are best understood by an example: The following function
		344	will change the current timezone to "Antarctica/South_Pole", which
		345	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		346	which remember/change the current timezone and restore the previous
		347	value, respectively, the timezone is only changes for the coroutine that
		348	installed those handlers.
		349
		350	use POSIX qw(tzset);
		351
		352	async {
		353	my $old_tz; # store outside TZ value here
		354
		355	Coro::on_enter {
		356	$old_tz = $ENV{TZ}; # remember the old value
		357
		358	$ENV{TZ} = "Antarctica/South_Pole";
		359	tzset; # enable new value
264	};	360	};
265		361
266	# call schedule until event occurred.	362	Coro::on_leave {
267	# in case we are woken up for other reasons	363	$ENV{TZ} = $old_tz;
268	# (current still defined), loop.	364	tzset; # restore old value
269	Coro::schedule while $current;	365	};
		366
		367	# at this place, the timezone is Antarctica/South_Pole,
		368	# without disturbing the TZ of any other coroutine.
270	}	369	};
271		370
272	=item cede	371	This can be used to localise about any resource (locale, uid, current
273		372	working directory etc.) to a block, despite the existance of other
274	"Cede" to other coroutines. This function puts the current coroutine into the	373	coroutines.
275	ready queue and calls C<schedule>, which has the effect of giving up the
276	current "timeslice" to other coroutines of the same or higher priority.
277
278	=item Coro::cede_notself
279
280	Works like cede, but is not exported by default and will cede to any
281	coroutine, regardless of priority, once.
282
283	=item terminate [arg...]
284
285	Terminates the current coroutine with the given status values (see L<cancel>).
286		374
287	=item killall	375	=item killall
288		376
289	Kills/terminates/cancels all coroutines except the currently running	377	Kills/terminates/cancels all coroutines except the currently running one.
290	one. This is useful after a fork, either in the child or the parent, as
291	usually only one of them should inherit the running coroutines.
292		378
293	=cut	379	Note that while this will try to free some of the main interpreter
		380	resources if the calling coroutine isn't the main coroutine, but one
		381	cannot free all of them, so if a coroutine that is not the main coroutine
		382	calls this function, there will be some one-time resource leak.
294		383
295	sub terminate {	384	=cut
296	$current->cancel (@_);
297	}
298		385
299	sub killall {	386	sub killall {
300	for (Coro::State::list) {	387	for (Coro::State::list) {
301	$_->cancel	388	$_->cancel
302	if $_ != $current && UNIVERSAL::isa $_, "Coro";	389	if $_ != $current && UNIVERSAL::isa $_, "Coro";
303	}	390	}
304	}	391	}
305		392
306	=back	393	=back
307		394
308	=head2 COROUTINE METHODS	395	=head1 COROUTINE OBJECT METHODS
309		396
310	These are the methods you can call on coroutine objects.	397	These are the methods you can call on coroutine objects (or to create
		398	them).
311		399
312	=over 4	400	=over 4
313		401
314	=item new Coro \&sub [, @args...]	402	=item new Coro \&sub [, @args...]
315		403
316	Create a new coroutine and return it. When the sub returns the coroutine	404	Create a new coroutine and return it. When the sub returns, the coroutine
317	automatically terminates as if C<terminate> with the returned values were	405	automatically terminates as if C<terminate> with the returned values were
318	called. To make the coroutine run you must first put it into the ready queue	406	called. To make the coroutine run you must first put it into the ready
319	by calling the ready method.	407	queue by calling the ready method.
320		408
321	See C<async> and C<Coro::State::new> for additional info about the	409	See C<async> and C<Coro::State::new> for additional info about the
322	coroutine environment.	410	coroutine environment.
323		411
324	=cut	412	=cut
325		413
326	sub _run_coro {	414	sub _coro_run {
327	terminate &{+shift};	415	terminate &{+shift};
328	}	416	}
329		417
330	sub new {
331	my $class = shift;
332
333	$class->SUPER::new (\&_run_coro, @_)
334	}
335
336	=item $success = $coroutine->ready	418	=item $success = $coroutine->ready
337		419
338	Put the given coroutine into the ready queue (according to it's priority)	420	Put the given coroutine into the end of its ready queue (there is one
339	and return true. If the coroutine is already in the ready queue, do nothing	421	queue for each priority) and return true. If the coroutine is already in
340	and return false.	422	the ready queue, do nothing and return false.
		423
		424	This ensures that the scheduler will resume this coroutine automatically
		425	once all the coroutines of higher priority and all coroutines of the same
		426	priority that were put into the ready queue earlier have been resumed.
341		427
342	=item $is_ready = $coroutine->is_ready	428	=item $is_ready = $coroutine->is_ready
343		429
344	Return wether the coroutine is currently the ready queue or not,	430	Return whether the coroutine is currently the ready queue or not,
345		431
346	=item $coroutine->cancel (arg...)	432	=item $coroutine->cancel (arg...)
347		433
348	Terminates the given coroutine and makes it return the given arguments as	434	Terminates the given coroutine and makes it return the given arguments as
349	status (default: the empty list). Never returns if the coroutine is the	435	status (default: the empty list). Never returns if the coroutine is the
…		…
351		437
352	=cut	438	=cut
353		439
354	sub cancel {	440	sub cancel {
355	my $self = shift;	441	my $self = shift;
356	$self->{_status} = [@_];
357		442
358	if ($current == $self) {	443	if ($current == $self) {
359	push @destroy, $self;	444	terminate @_;
360	$manager->ready;
361	&schedule while 1;
362	} else {	445	} else {
		446	$self->{_status} = [@_];
363	$self->_cancel;	447	$self->_cancel;
364	}	448	}
365	}	449	}
366		450
		451	=item $coroutine->schedule_to
		452
		453	Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
		454	of continuing with the next coro from the ready queue, always switch to
		455	the given coroutine object (regardless of priority etc.). The readyness
		456	state of that coroutine isn't changed.
		457
		458	This is an advanced method for special cases - I'd love to hear about any
		459	uses for this one.
		460
		461	=item $coroutine->cede_to
		462
		463	Like C<schedule_to>, but puts the current coroutine into the ready
		464	queue. This has the effect of temporarily switching to the given
		465	coroutine, and continuing some time later.
		466
		467	This is an advanced method for special cases - I'd love to hear about any
		468	uses for this one.
		469
		470	=item $coroutine->throw ([$scalar])
		471
		472	If C<$throw> is specified and defined, it will be thrown as an exception
		473	inside the coroutine at the next convenient point in time. Otherwise
		474	clears the exception object.
		475
		476	Coro will check for the exception each time a schedule-like-function
		477	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		478	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		479	detect this case and return early in case an exception is pending.
		480
		481	The exception object will be thrown "as is" with the specified scalar in
		482	C<$@>, i.e. if it is a string, no line number or newline will be appended
		483	(unlike with C<die>).
		484
		485	This can be used as a softer means than C<cancel> to ask a coroutine to
		486	end itself, although there is no guarantee that the exception will lead to
		487	termination, and if the exception isn't caught it might well end the whole
		488	program.
		489
		490	You might also think of C<throw> as being the moral equivalent of
		491	C<kill>ing a coroutine with a signal (in this case, a scalar).
		492
367	=item $coroutine->join	493	=item $coroutine->join
368		494
369	Wait until the coroutine terminates and return any values given to the	495	Wait until the coroutine terminates and return any values given to the
370	C<terminate> or C<cancel> functions. C<join> can be called concurrently	496	C<terminate> or C<cancel> functions. C<join> can be called concurrently
371	from multiple coroutines.	497	from multiple coroutines, and all will be resumed and given the status
		498	return once the C<$coroutine> terminates.
372		499
373	=cut	500	=cut
374		501
375	sub join {	502	sub join {
376	my $self = shift;	503	my $self = shift;
…		…
391		518
392	=item $coroutine->on_destroy (\&cb)	519	=item $coroutine->on_destroy (\&cb)
393		520
394	Registers a callback that is called when this coroutine gets destroyed,	521	Registers a callback that is called when this coroutine gets destroyed,
395	but before it is joined. The callback gets passed the terminate arguments,	522	but before it is joined. The callback gets passed the terminate arguments,
396	if any.	523	if any, and I<must not> die, under any circumstances.
397		524
398	=cut	525	=cut
399		526
400	sub on_destroy {	527	sub on_destroy {
401	my ($self, $cb) = @_;	528	my ($self, $cb) = @_;
…		…
431	higher values mean lower priority, just as in unix).	558	higher values mean lower priority, just as in unix).
432		559
433	=item $olddesc = $coroutine->desc ($newdesc)	560	=item $olddesc = $coroutine->desc ($newdesc)
434		561
435	Sets (or gets in case the argument is missing) the description for this	562	Sets (or gets in case the argument is missing) the description for this
436	coroutine. This is just a free-form string you can associate with a coroutine.	563	coroutine. This is just a free-form string you can associate with a
		564	coroutine.
437		565
438	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You	566	This method simply sets the C<< $coroutine->{desc} >> member to the given
439	can modify this member directly if you wish.	567	string. You can modify this member directly if you wish.
440
441	=item $coroutine->throw ([$scalar])
442
443	If C<$throw> is specified and defined, it will be thrown as an exception
444	inside the coroutine at the next convinient point in time (usually after
445	it gains control at the next schedule/transfer/cede). Otherwise clears the
446	exception object.
447
448	The exception object will be thrown "as is" with the specified scalar in
449	C<$@>, i.e. if it is a string, no line number or newline will be appended
450	(unlike with C<die>).
451
452	This can be used as a softer means than C<cancel> to ask a coroutine to
453	end itself, although there is no guarentee that the exception will lead to
454	termination, and if the exception isn't caught it might well end the whole
455	program.
456		568
457	=cut	569	=cut
458		570
459	sub desc {	571	sub desc {
460	my $old = $_[0]{desc};	572	my $old = $_[0]{desc};
461	$_[0]{desc} = $_[1] if @_ > 1;	573	$_[0]{desc} = $_[1] if @_ > 1;
462	$old;	574	$old;
463	}	575	}
464		576
		577	sub transfer {
		578	require Carp;
		579	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		580	}
		581
465	=back	582	=back
466		583
467	=head2 GLOBAL FUNCTIONS	584	=head1 GLOBAL FUNCTIONS
468		585
469	=over 4	586	=over 4
470		587
471	=item Coro::nready	588	=item Coro::nready
472		589
473	Returns the number of coroutines that are currently in the ready state,	590	Returns the number of coroutines that are currently in the ready state,
474	i.e. that can be switched to. The value C<0> means that the only runnable	591	i.e. that can be switched to by calling C<schedule> directory or
		592	indirectly. The value C<0> means that the only runnable coroutine is the
475	coroutine is the currently running one, so C<cede> would have no effect,	593	currently running one, so C<cede> would have no effect, and C<schedule>
476	and C<schedule> would cause a deadlock unless there is an idle handler	594	would cause a deadlock unless there is an idle handler that wakes up some
477	that wakes up some coroutines.	595	coroutines.
478		596
479	=item my $guard = Coro::guard { ... }	597	=item my $guard = Coro::guard { ... }
480		598
481	This creates and returns a guard object. Nothing happens until the object	599	This function still exists, but is deprecated. Please use the
482	gets destroyed, in which case the codeblock given as argument will be	600	C<Guard::guard> function instead.
483	executed. This is useful to free locks or other resources in case of a
484	runtime error or when the coroutine gets canceled, as in both cases the
485	guard block will be executed. The guard object supports only one method,
486	C<< ->cancel >>, which will keep the codeblock from being executed.
487		601
488	Example: set some flag and clear it again when the coroutine gets canceled
489	or the function returns:
490
491	sub do_something {
492	my $guard = Coro::guard { $busy = 0 };
493	$busy = 1;
494
495	# do something that requires $busy to be true
496	}
497
498	=cut	602	=cut
499		603
500	sub guard(&) {	604	BEGIN { *guard = \&Guard::guard }
501	bless \(my $cb = $_[0]), "Coro::guard"
502	}
503
504	sub Coro::guard::cancel {
505	${$_[0]} = sub { };
506	}
507
508	sub Coro::guard::DESTROY {
509	${$_[0]}->();
510	}
511
512		605
513	=item unblock_sub { ... }	606	=item unblock_sub { ... }
514		607
515	This utility function takes a BLOCK or code reference and "unblocks" it,	608	This utility function takes a BLOCK or code reference and "unblocks" it,
516	returning the new coderef. This means that the new coderef will return	609	returning a new coderef. Unblocking means that calling the new coderef
517	immediately without blocking, returning nothing, while the original code	610	will return immediately without blocking, returning nothing, while the
518	ref will be called (with parameters) from within its own coroutine.	611	original code ref will be called (with parameters) from within another
		612	coroutine.
519		613
520	The reason this function exists is that many event libraries (such as the	614	The reason this function exists is that many event libraries (such as the
521	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	615	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
522	of thread-safety). This means you must not block within event callbacks,	616	of reentrancy). This means you must not block within event callbacks,
523	otherwise you might suffer from crashes or worse.	617	otherwise you might suffer from crashes or worse. The only event library
		618	currently known that is safe to use without C<unblock_sub> is L<EV>.
524		619
525	This function allows your callbacks to block by executing them in another	620	This function allows your callbacks to block by executing them in another
526	coroutine where it is safe to block. One example where blocking is handy	621	coroutine where it is safe to block. One example where blocking is handy
527	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	622	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
528	disk.	623	disk, for example.
529		624
530	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	625	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
531	creating event callbacks that want to block.	626	creating event callbacks that want to block.
		627
		628	If your handler does not plan to block (e.g. simply sends a message to
		629	another coroutine, or puts some other coroutine into the ready queue),
		630	there is no reason to use C<unblock_sub>.
		631
		632	Note that you also need to use C<unblock_sub> for any other callbacks that
		633	are indirectly executed by any C-based event loop. For example, when you
		634	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		635	provides callbacks that are the result of some event callback, then you
		636	must not block either, or use C<unblock_sub>.
532		637
533	=cut	638	=cut
534		639
535	our @unblock_queue;	640	our @unblock_queue;
536		641
…		…
539	# return immediately and can be reused) and because we cannot cede	644	# return immediately and can be reused) and because we cannot cede
540	# inside an event callback.	645	# inside an event callback.
541	our $unblock_scheduler = new Coro sub {	646	our $unblock_scheduler = new Coro sub {
542	while () {	647	while () {
543	while (my $cb = pop @unblock_queue) {	648	while (my $cb = pop @unblock_queue) {
544	# this is an inlined copy of async_pool	649	&async_pool (@$cb);
545	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
546		650
547	$coro->{_invoke} = $cb;
548	$coro->ready;
549	cede; # for short-lived callbacks, this reduces pressure on the coro pool	651	# for short-lived callbacks, this reduces pressure on the coro pool
		652	# as the chance is very high that the async_poll coro will be back
		653	# in the idle state when cede returns
		654	cede;
550	}	655	}
551	schedule; # sleep well	656	schedule; # sleep well
552	}	657	}
553	};	658	};
554	$unblock_scheduler->desc ("[unblock_sub scheduler]");	659	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
555		660
556	sub unblock_sub(&) {	661	sub unblock_sub(&) {
557	my $cb = shift;	662	my $cb = shift;
558		663
559	sub {	664	sub {
560	unshift @unblock_queue, [$cb, @_];	665	unshift @unblock_queue, [$cb, @_];
561	$unblock_scheduler->ready;	666	$unblock_scheduler->ready;
562	}	667	}
563	}	668	}
564		669
		670	=item $cb = Coro::rouse_cb
		671
		672	Create and return a "rouse callback". That's a code reference that,
		673	when called, will remember a copy of its arguments and notify the owner
		674	coroutine of the callback.
		675
		676	See the next function.
		677
		678	=item @args = Coro::rouse_wait [$cb]
		679
		680	Wait for the specified rouse callback (or the last one that was created in
		681	this coroutine).
		682
		683	As soon as the callback is invoked (or when the callback was invoked
		684	before C<rouse_wait>), it will return the arguments originally passed to
		685	the rouse callback.
		686
		687	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		688
565	=back	689	=back
566		690
567	=cut	691	=cut
568		692
569	1;	693	1;
570		694
		695	=head1 HOW TO WAIT FOR A CALLBACK
		696
		697	It is very common for a coroutine to wait for some callback to be
		698	called. This occurs naturally when you use coroutines in an otherwise
		699	event-based program, or when you use event-based libraries.
		700
		701	These typically register a callback for some event, and call that callback
		702	when the event occured. In a coroutine, however, you typically want to
		703	just wait for the event, simplyifying things.
		704
		705	For example C<< AnyEvent->child >> registers a callback to be called when
		706	a specific child has exited:
		707
		708	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		709
		710	But from withina coroutine, you often just want to write this:
		711
		712	my $status = wait_for_child $pid;
		713
		714	Coro offers two functions specifically designed to make this easy,
		715	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		716
		717	The first function, C<rouse_cb>, generates and returns a callback that,
		718	when invoked, will save its arguments and notify the coroutine that
		719	created the callback.
		720
		721	The second function, C<rouse_wait>, waits for the callback to be called
		722	(by calling C<schedule> to go to sleep) and returns the arguments
		723	originally passed to the callback.
		724
		725	Using these functions, it becomes easy to write the C<wait_for_child>
		726	function mentioned above:
		727
		728	sub wait_for_child($) {
		729	my ($pid) = @_;
		730
		731	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		732
		733	my ($rpid, $rstatus) = Coro::rouse_wait;
		734	$rstatus
		735	}
		736
		737	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		738	you can roll your own, using C<schedule>:
		739
		740	sub wait_for_child($) {
		741	my ($pid) = @_;
		742
		743	# store the current coroutine in $current,
		744	# and provide result variables for the closure passed to ->child
		745	my $current = $Coro::current;
		746	my ($done, $rstatus);
		747
		748	# pass a closure to ->child
		749	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		750	$rstatus = $_[1]; # remember rstatus
		751	$done = 1; # mark $rstatus as valud
		752	});
		753
		754	# wait until the closure has been called
		755	schedule while !$done;
		756
		757	$rstatus
		758	}
		759
		760
571	=head1 BUGS/LIMITATIONS	761	=head1 BUGS/LIMITATIONS
572		762
573	- you must make very sure that no coro is still active on global	763	=over 4
574	destruction. very bad things might happen otherwise (usually segfaults).
575		764
		765	=item fork with pthread backend
		766
		767	When Coro is compiled using the pthread backend (which isn't recommended
		768	but required on many BSDs as their libcs are completely broken), then
		769	coroutines will not survive a fork. There is no known workaround except to
		770	fix your libc and use a saner backend.
		771
		772	=item perl process emulation ("threads")
		773
576	- this module is not thread-safe. You should only ever use this module	774	This module is not perl-pseudo-thread-safe. You should only ever use this
577	from the same thread (this requirement might be loosened in the future	775	module from the first thread (this requirement might be removed in the
578	to allow per-thread schedulers, but Coro::State does not yet allow	776	future to allow per-thread schedulers, but Coro::State does not yet allow
579	this).	777	this). I recommend disabling thread support and using processes, as having
		778	the windows process emulation enabled under unix roughly halves perl
		779	performance, even when not used.
		780
		781	=item coroutine switching not signal safe
		782
		783	You must not switch to another coroutine from within a signal handler
		784	(only relevant with %SIG - most event libraries provide safe signals).
		785
		786	That means you I<MUST NOT> call any function that might "block" the
		787	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		788	anything that calls those. Everything else, including calling C<ready>,
		789	works.
		790
		791	=back
		792
580		793
581	=head1 SEE ALSO	794	=head1 SEE ALSO
582		795
583	Lower level Configuration, Coroutine Environment: L<Coro::State>.	796	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
584		797
585	Debugging: L<Coro::Debug>.	798	Debugging: L<Coro::Debug>.
586		799
587	Support/Utility: L<Coro::Specific>, L<Coro::Util>.	800	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
588		801
589	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	802	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		803	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
590		804
591	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>.	805	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
592		806
593	Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>.	807	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		808	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		809	L<Coro::Select>.
594		810
595	Embedding: L<Coro::MakeMaker>.	811	XS API: L<Coro::MakeMaker>.
		812
		813	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
596		814
597	=head1 AUTHOR	815	=head1 AUTHOR
598		816
599	Marc Lehmann <schmorp@schmorp.de>	817	Marc Lehmann <schmorp@schmorp.de>
600	http://home.schmorp.de/	818	http://home.schmorp.de/

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Revision 1.247 by root, Mon Dec 15 02:07:11 2008 UTC