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

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Revision 1.145 by root, Wed Oct 3 16:03:17 2007 UTC vs.
Revision 1.245 by root, Sun Dec 14 19:52:58 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
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	For a tutorial-style introduction, please read the L<Coro::Intro>
24	to threads but don't run in parallel at the same time even on SMP	32	manpage. This manpage mainly contains reference information.
25	machines. The specific flavor of coroutine used in this module also
26	guarantees you that it will not switch between coroutines unless
27	necessary, at easily-identified points in your program, so locking and
28	parallel access are rarely an issue, making coroutine programming much
29	safer than threads programming.
30		33
31	(Perl, however, does not natively support real threads but instead does a	34	This module collection manages continuations in general, most often
32	very slow and memory-intensive emulation of processes using threads. This	35	in the form of cooperative threads (also called coroutines in the
33	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.
34		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
35	In this module, coroutines are defined as "callchain + lexical variables +	56	In this module, a thread is defined as "callchain + lexical variables +
36	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	57	@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,
37	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
38	variables.	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.
39		63
40	=cut	64	=cut
41		65
42	package Coro;	66	package Coro;
43		67
44	use strict;	68	use strict qw(vars subs);
45	no warnings "uninitialized";	69	no warnings "uninitialized";
46		70
47	use Coro::State;	71	use Coro::State;
48		72
49	use base qw(Coro::State Exporter);	73	use base qw(Coro::State Exporter);
50		74
51	our $idle; # idle handler	75	our $idle; # idle handler
52	our $main; # main coroutine	76	our $main; # main coroutine
53	our $current; # current coroutine	77	our $current; # current coroutine
54		78
55	our $VERSION = '4.0';	79	our $VERSION = 5.13;
56		80
57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	81	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
58	our %EXPORT_TAGS = (	82	our %EXPORT_TAGS = (
59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	83	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60	);	84	);
61	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	85	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
62		86
63	{	87	=head1 GLOBAL VARIABLES
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		88
97	=over 4	89	=over 4
98		90
99	=item $main	91	=item $Coro::main
100		92
101	This coroutine represents the main program.	93	This variable stores the coroutine object that represents the main
		94	program. While you cna C<ready> it and do most other things you can do to
		95	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		96	whether you are running in the main program or not.
102		97
103	=cut	98	=cut
104		99
105	$main = new Coro;	100	# $main is now being initialised by Coro::State
106		101
107	=item $current (or as function: current)	102	=item $Coro::current
108		103
109	The current coroutine (the last coroutine switched to). The initial value	104	The coroutine object representing the current coroutine (the last
		105	coroutine that the Coro scheduler switched to). The initial value is
110	is C<$main> (of course).	106	C<$Coro::main> (of course).
111		107
112	This variable is B<strictly> I<read-only>. It is provided for performance	108	This variable is B<strictly> I<read-only>. You can take copies of the
113	reasons. If performance is not essential you are encouraged to use the	109	value stored in it and use it as any other coroutine object, but you must
114	C<Coro::current> function instead.	110	not otherwise modify the variable itself.
115		111
116	=cut	112	=cut
117		113
118	$main->{desc} = "[main::]";
119
120	# maybe some other module used Coro::Specific before...
121	$main->{_specific} = $current->{_specific}
122	if $current;
123
124	_set_current $main;
125
126	sub current() { $current }	114	sub current() { $current } # [DEPRECATED]
127		115
128	=item $idle	116	=item $Coro::idle
129		117
		118	This variable is mainly useful to integrate Coro into event loops. It is
		119	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		120	pretty low-level functionality.
		121
		122	This variable stores either a coroutine or a callback.
		123
130	A callback that is called whenever the scheduler finds no ready coroutines	124	If it is a callback, the it is called whenever the scheduler finds no
131	to run. The default implementation prints "FATAL: deadlock detected" and	125	ready coroutines to run. The default implementation prints "FATAL:
132	exits, because the program has no other way to continue.	126	deadlock detected" and exits, because the program has no other way to
		127	continue.
133		128
		129	If it is a coroutine object, then this object will be readied (without
		130	invoking any ready hooks, however) when the scheduler finds no other ready
		131	coroutines to run.
		132
134	This hook is overwritten by modules such as C<Coro::Timer> and	133	This hook is overwritten by modules such as C<Coro::EV> and
135	C<Coro::Event> to wait on an external event that hopefully wake up a	134	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
136	coroutine so the scheduler can run it.	135	coroutine so the scheduler can run it.
137		136
		137	Note that the callback I<must not>, under any circumstances, block
		138	the current coroutine. Normally, this is achieved by having an "idle
		139	coroutine" that calls the event loop and then blocks again, and then
		140	readying that coroutine in the idle handler, or by simply placing the idle
		141	coroutine in this variable.
		142
		143	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		144	technique.
		145
138	Please note that if your callback recursively invokes perl (e.g. for event	146	Please note that if your callback recursively invokes perl (e.g. for event
139	handlers), then it must be prepared to be called recursively.	147	handlers), then it must be prepared to be called recursively itself.
140		148
141	=cut	149	=cut
142		150
143	$idle = sub {	151	$idle = sub {
144	require Carp;	152	require Carp;
145	Carp::croak ("FATAL: deadlock detected");	153	Carp::croak ("FATAL: deadlock detected");
146	};	154	};
147		155
148	sub _cancel {
149	my ($self) = @_;
150
151	# free coroutine data and mark as destructed
152	$self->_destroy
153	or return;
154
155	# call all destruction callbacks
156	$_->(@{$self->{_status}})
157	for @{(delete $self->{_on_destroy}) \|\| []};
158	}
159
160	# this coroutine is necessary because a coroutine	156	# this coroutine is necessary because a coroutine
161	# cannot destroy itself.	157	# cannot destroy itself.
162	my @destroy;	158	our @destroy;
163	my $manager;	159	our $manager;
164		160
165	$manager = new Coro sub {	161	$manager = new Coro sub {
166	while () {	162	while () {
167	(shift @destroy)->_cancel	163	Coro::_cancel shift @destroy
168	while @destroy;	164	while @destroy;
169		165
170	&schedule;	166	&schedule;
171	}	167	}
172	};	168	};
173	$manager->desc ("[coro manager]");	169	$manager->{desc} = "[coro manager]";
174	$manager->prio (PRIO_MAX);	170	$manager->prio (PRIO_MAX);
175		171
176	# static methods. not really.
177
178	=back	172	=back
179		173
180	=head2 STATIC METHODS	174	=head1 SIMPLE COROUTINE CREATION
181
182	Static methods are actually functions that operate on the current coroutine only.
183		175
184	=over 4	176	=over 4
185		177
186	=item async { ... } [@args...]	178	=item async { ... } [@args...]
187		179
188	Create a new asynchronous coroutine and return it's coroutine object	180	Create a new coroutine and return its coroutine object (usually
189	(usually unused). When the sub returns the new coroutine is automatically	181	unused). The coroutine will be put into the ready queue, so
		182	it will start running automatically on the next scheduler run.
		183
		184	The first argument is a codeblock/closure that should be executed in the
		185	coroutine. When it returns argument returns the coroutine is automatically
190	terminated.	186	terminated.
191		187
		188	The remaining arguments are passed as arguments to the closure.
		189
192	See the C<Coro::State::new> constructor for info about the coroutine	190	See the C<Coro::State::new> constructor for info about the coroutine
193	environment.	191	environment in which coroutines are executed.
194		192
195	Calling C<exit> in a coroutine will do the same as calling exit outside	193	Calling C<exit> in a coroutine will do the same as calling exit outside
196	the coroutine. Likewise, when the coroutine dies, the program will exit,	194	the coroutine. Likewise, when the coroutine dies, the program will exit,
197	just as it would in the main program.	195	just as it would in the main program.
198		196
		197	If you do not want that, you can provide a default C<die> handler, or
		198	simply avoid dieing (by use of C<eval>).
		199
199	# create a new coroutine that just prints its arguments	200	Example: Create a new coroutine that just prints its arguments.
		201
200	async {	202	async {
201	print "@_\n";	203	print "@_\n";
202	} 1,2,3,4;	204	} 1,2,3,4;
203		205
204	=cut	206	=cut
210	}	212	}
211		213
212	=item async_pool { ... } [@args...]	214	=item async_pool { ... } [@args...]
213		215
214	Similar to C<async>, but uses a coroutine pool, so you should not call	216	Similar to C<async>, but uses a coroutine pool, so you should not call
215	terminate or join (although you are allowed to), and you get a coroutine	217	terminate or join on it (although you are allowed to), and you get a
216	that might have executed other code already (which can be good or bad :).	218	coroutine that might have executed other code already (which can be good
		219	or bad :).
217		220
		221	On the plus side, this function is about twice as fast as creating (and
		222	destroying) a completely new coroutine, so if you need a lot of generic
		223	coroutines in quick successsion, use C<async_pool>, not C<async>.
		224
218	Also, the block is executed in an C<eval> context and a warning will be	225	The code block is executed in an C<eval> context and a warning will be
219	issued in case of an exception instead of terminating the program, as	226	issued in case of an exception instead of terminating the program, as
220	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>	227	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
221	will not work in the expected way, unless you call terminate or cancel,	228	will not work in the expected way, unless you call terminate or cancel,
222	which somehow defeats the purpose of pooling.	229	which somehow defeats the purpose of pooling (but is fine in the
		230	exceptional case).
223		231
224	The priority will be reset to C<0> after each job, otherwise the coroutine	232	The priority will be reset to C<0> after each run, tracing will be
225	will be re-used "as-is".	233	disabled, the description will be reset and the default output filehandle
		234	gets restored, so you can change all these. Otherwise the coroutine will
		235	be re-used "as-is": most notably if you change other per-coroutine global
		236	stuff such as C<$/> you I<must needs> revert that change, which is most
		237	simply done by using local as in: C<< local $/ >>.
226		238
227	The pool size is limited to 8 idle coroutines (this can be adjusted by	239	The idle pool size is limited to C<8> idle coroutines (this can be
228	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as	240	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
229	required.	241	coros as required.
230		242
231	If you are concerned about pooled coroutines growing a lot because a	243	If you are concerned about pooled coroutines growing a lot because a
232	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool	244	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
233	{ terminate }> once per second or so to slowly replenish the pool. In	245	{ terminate }> once per second or so to slowly replenish the pool. In
234	addition to that, when the stacks used by a handler grows larger than 16kb	246	addition to that, when the stacks used by a handler grows larger than 32kb
235	(adjustable with $Coro::POOL_RSS) it will also exit.	247	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
236		248
237	=cut	249	=cut
238		250
239	our $POOL_SIZE = 8;	251	our $POOL_SIZE = 8;
240	our $POOL_RSS = 16 * 1024;	252	our $POOL_RSS = 32 * 1024;
241	our @async_pool;	253	our @async_pool;
242		254
243	sub pool_handler {	255	sub pool_handler {
244	my $cb;
245
246	while () {	256	while () {
247	eval {	257	eval {
248	while () {	258	&{&_pool_handler} while 1;
249	_pool_1 $cb;
250	&$cb;
251	_pool_2 $cb;
252	&schedule;
253	}
254	};	259	};
255		260
256	last if $@ eq "\3terminate\2\n";
257	warn $@ if $@;	261	warn $@ if $@;
258	}	262	}
259	}	263	}
260		264
261	sub async_pool(&@) {	265	=back
262	# this is also inlined into the unlock_scheduler
263	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
264		266
265	$coro->{_invoke} = [@_];	267	=head1 STATIC METHODS
266	$coro->ready;
267		268
268	$coro	269	Static methods are actually functions that implicitly operate on the
269	}	270	current coroutine.
		271
		272	=over 4
270		273
271	=item schedule	274	=item schedule
272		275
273	Calls the scheduler. Please note that the current coroutine will not be put	276	Calls the scheduler. The scheduler will find the next coroutine that is
		277	to be run from the ready queue and switches to it. The next coroutine
		278	to be run is simply the one with the highest priority that is longest
		279	in its ready queue. If there is no coroutine ready, it will clal the
		280	C<$Coro::idle> hook.
		281
		282	Please note that the current coroutine will I<not> be put into the ready
274	into the ready queue, so calling this function usually means you will	283	queue, so calling this function usually means you will never be called
275	never be called again unless something else (e.g. an event handler) calls	284	again unless something else (e.g. an event handler) calls C<< ->ready >>,
276	ready.	285	thus waking you up.
277		286
278	The canonical way to wait on external events is this:	287	This makes C<schedule> I<the> generic method to use to block the current
		288	coroutine and wait for events: first you remember the current coroutine in
		289	a variable, then arrange for some callback of yours to call C<< ->ready
		290	>> on that once some event happens, and last you call C<schedule> to put
		291	yourself to sleep. Note that a lot of things can wake your coroutine up,
		292	so you need to check whether the event indeed happened, e.g. by storing the
		293	status in a variable.
279		294
280	{	295	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
281	# remember current coroutine
282	my $current = $Coro::current;
283
284	# register a hypothetical event handler
285	on_event_invoke sub {
286	# wake up sleeping coroutine
287	$current->ready;
288	undef $current;
289	};
290
291	# call schedule until event occurred.
292	# in case we are woken up for other reasons
293	# (current still defined), loop.
294	Coro::schedule while $current;
295	}
296		296
297	=item cede	297	=item cede
298		298
299	"Cede" to other coroutines. This function puts the current coroutine into the	299	"Cede" to other coroutines. This function puts the current coroutine into
300	ready queue and calls C<schedule>, which has the effect of giving up the	300	the ready queue and calls C<schedule>, which has the effect of giving
301	current "timeslice" to other coroutines of the same or higher priority.	301	up the current "timeslice" to other coroutines of the same or higher
		302	priority. Once your coroutine gets its turn again it will automatically be
		303	resumed.
302		304
303	Returns true if at least one coroutine switch has happened.	305	This function is often called C<yield> in other languages.
304		306
305	=item Coro::cede_notself	307	=item Coro::cede_notself
306		308
307	Works like cede, but is not exported by default and will cede to any	309	Works like cede, but is not exported by default and will cede to I<any>
308	coroutine, regardless of priority, once.	310	coroutine, regardless of priority. This is useful sometimes to ensure
309		311	progress is made.
310	Returns true if at least one coroutine switch has happened.
311		312
312	=item terminate [arg...]	313	=item terminate [arg...]
313		314
314	Terminates the current coroutine with the given status values (see L<cancel>).	315	Terminates the current coroutine with the given status values (see L<cancel>).
315		316
316	=item killall	317	=item killall
317		318
318	Kills/terminates/cancels all coroutines except the currently running	319	Kills/terminates/cancels all coroutines except the currently running
319	one. This is useful after a fork, either in the child or the parent, as	320	one. This can be useful after a fork, either in the child or the parent,
320	usually only one of them should inherit the running coroutines.	321	as usually only one of them should inherit the running coroutines.
321		322
322	=cut	323	Note that in the implementation, destructors run as normal, making this
		324	function not so useful after a fork. Future versions of this function
		325	might try to free resources without running any code.
323		326
324	sub terminate {	327	Note that while this will try to free some of the main programs resources,
325	$current->cancel (@_);	328	you cannot free all of them, so if a coroutine that is not the main
326	}	329	program calls this function, there will be some one-time resource leak.
		330
		331	=cut
327		332
328	sub killall {	333	sub killall {
329	for (Coro::State::list) {	334	for (Coro::State::list) {
330	$_->cancel	335	$_->cancel
331	if $_ != $current && UNIVERSAL::isa $_, "Coro";	336	if $_ != $current && UNIVERSAL::isa $_, "Coro";
332	}	337	}
333	}	338	}
334		339
335	=back	340	=back
336		341
337	# dynamic methods
338
339	=head2 COROUTINE METHODS	342	=head1 COROUTINE OBJECT METHODS
340		343
341	These are the methods you can call on coroutine objects.	344	These are the methods you can call on coroutine objects (or to create
		345	them).
342		346
343	=over 4	347	=over 4
344		348
345	=item new Coro \&sub [, @args...]	349	=item new Coro \&sub [, @args...]
346		350
347	Create a new coroutine and return it. When the sub returns the coroutine	351	Create a new coroutine and return it. When the sub returns, the coroutine
348	automatically terminates as if C<terminate> with the returned values were	352	automatically terminates as if C<terminate> with the returned values were
349	called. To make the coroutine run you must first put it into the ready queue	353	called. To make the coroutine run you must first put it into the ready
350	by calling the ready method.	354	queue by calling the ready method.
351		355
352	See C<async> and C<Coro::State::new> for additional info about the	356	See C<async> and C<Coro::State::new> for additional info about the
353	coroutine environment.	357	coroutine environment.
354		358
355	=cut	359	=cut
356		360
357	sub _run_coro {	361	sub _coro_run {
358	terminate &{+shift};	362	terminate &{+shift};
359	}	363	}
360		364
361	sub new {
362	my $class = shift;
363
364	$class->SUPER::new (\&_run_coro, @_)
365	}
366
367	=item $success = $coroutine->ready	365	=item $success = $coroutine->ready
368		366
369	Put the given coroutine into the ready queue (according to it's priority)	367	Put the given coroutine into the end of its ready queue (there is one
370	and return true. If the coroutine is already in the ready queue, do nothing	368	queue for each priority) and return true. If the coroutine is already in
371	and return false.	369	the ready queue, do nothing and return false.
		370
		371	This ensures that the scheduler will resume this coroutine automatically
		372	once all the coroutines of higher priority and all coroutines of the same
		373	priority that were put into the ready queue earlier have been resumed.
372		374
373	=item $is_ready = $coroutine->is_ready	375	=item $is_ready = $coroutine->is_ready
374		376
375	Return wether the coroutine is currently the ready queue or not,	377	Return whether the coroutine is currently the ready queue or not,
376		378
377	=item $coroutine->cancel (arg...)	379	=item $coroutine->cancel (arg...)
378		380
379	Terminates the given coroutine and makes it return the given arguments as	381	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	382	status (default: the empty list). Never returns if the coroutine is the
…		…
382		384
383	=cut	385	=cut
384		386
385	sub cancel {	387	sub cancel {
386	my $self = shift;	388	my $self = shift;
387	$self->{_status} = [@_];
388		389
389	if ($current == $self) {	390	if ($current == $self) {
390	push @destroy, $self;	391	terminate @_;
391	$manager->ready;
392	&schedule while 1;
393	} else {	392	} else {
		393	$self->{_status} = [@_];
394	$self->_cancel;	394	$self->_cancel;
395	}	395	}
396	}	396	}
		397
		398	=item $coroutine->schedule_to
		399
		400	Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
		401	of continuing with the next coro from the ready queue, always switch to
		402	the given coroutine object (regardless of priority etc.). The readyness
		403	state of that coroutine isn't changed.
		404
		405	This is an advanced method for special cases - I'd love to hear about any
		406	uses for this one.
		407
		408	=item $coroutine->cede_to
		409
		410	Like C<schedule_to>, but puts the current coroutine into the ready
		411	queue. This has the effect of temporarily switching to the given
		412	coroutine, and continuing some time later.
		413
		414	This is an advanced method for special cases - I'd love to hear about any
		415	uses for this one.
		416
		417	=item $coroutine->throw ([$scalar])
		418
		419	If C<$throw> is specified and defined, it will be thrown as an exception
		420	inside the coroutine at the next convenient point in time. Otherwise
		421	clears the exception object.
		422
		423	Coro will check for the exception each time a schedule-like-function
		424	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		425	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		426	detect this case and return early in case an exception is pending.
		427
		428	The exception object will be thrown "as is" with the specified scalar in
		429	C<$@>, i.e. if it is a string, no line number or newline will be appended
		430	(unlike with C<die>).
		431
		432	This can be used as a softer means than C<cancel> to ask a coroutine to
		433	end itself, although there is no guarantee that the exception will lead to
		434	termination, and if the exception isn't caught it might well end the whole
		435	program.
		436
		437	You might also think of C<throw> as being the moral equivalent of
		438	C<kill>ing a coroutine with a signal (in this case, a scalar).
397		439
398	=item $coroutine->join	440	=item $coroutine->join
399		441
400	Wait until the coroutine terminates and return any values given to the	442	Wait until the coroutine terminates and return any values given to the
401	C<terminate> or C<cancel> functions. C<join> can be called concurrently	443	C<terminate> or C<cancel> functions. C<join> can be called concurrently
402	from multiple coroutines.	444	from multiple coroutines, and all will be resumed and given the status
		445	return once the C<$coroutine> terminates.
403		446
404	=cut	447	=cut
405		448
406	sub join {	449	sub join {
407	my $self = shift;	450	my $self = shift;
…		…
422		465
423	=item $coroutine->on_destroy (\&cb)	466	=item $coroutine->on_destroy (\&cb)
424		467
425	Registers a callback that is called when this coroutine gets destroyed,	468	Registers a callback that is called when this coroutine gets destroyed,
426	but before it is joined. The callback gets passed the terminate arguments,	469	but before it is joined. The callback gets passed the terminate arguments,
427	if any.	470	if any, and I<must not> die, under any circumstances.
428		471
429	=cut	472	=cut
430		473
431	sub on_destroy {	474	sub on_destroy {
432	my ($self, $cb) = @_;	475	my ($self, $cb) = @_;
…		…
462	higher values mean lower priority, just as in unix).	505	higher values mean lower priority, just as in unix).
463		506
464	=item $olddesc = $coroutine->desc ($newdesc)	507	=item $olddesc = $coroutine->desc ($newdesc)
465		508
466	Sets (or gets in case the argument is missing) the description for this	509	Sets (or gets in case the argument is missing) the description for this
467	coroutine. This is just a free-form string you can associate with a coroutine.	510	coroutine. This is just a free-form string you can associate with a
		511	coroutine.
468		512
469	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You	513	This method simply sets the C<< $coroutine->{desc} >> member to the given
470	can modify this member directly if you wish.	514	string. You can modify this member directly if you wish.
471		515
472	=cut	516	=cut
473		517
474	sub desc {	518	sub desc {
475	my $old = $_[0]{desc};	519	my $old = $_[0]{desc};
476	$_[0]{desc} = $_[1] if @_ > 1;	520	$_[0]{desc} = $_[1] if @_ > 1;
477	$old;	521	$old;
478	}	522	}
479		523
		524	sub transfer {
		525	require Carp;
		526	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		527	}
		528
480	=back	529	=back
481		530
482	=head2 GLOBAL FUNCTIONS	531	=head1 GLOBAL FUNCTIONS
483		532
484	=over 4	533	=over 4
485		534
486	=item Coro::nready	535	=item Coro::nready
487		536
488	Returns the number of coroutines that are currently in the ready state,	537	Returns the number of coroutines that are currently in the ready state,
489	i.e. that can be switched to. The value C<0> means that the only runnable	538	i.e. that can be switched to by calling C<schedule> directory or
		539	indirectly. The value C<0> means that the only runnable coroutine is the
490	coroutine is the currently running one, so C<cede> would have no effect,	540	currently running one, so C<cede> would have no effect, and C<schedule>
491	and C<schedule> would cause a deadlock unless there is an idle handler	541	would cause a deadlock unless there is an idle handler that wakes up some
492	that wakes up some coroutines.	542	coroutines.
493		543
494	=item my $guard = Coro::guard { ... }	544	=item my $guard = Coro::guard { ... }
495		545
496	This creates and returns a guard object. Nothing happens until the object	546	This function still exists, but is deprecated. Please use the
497	gets destroyed, in which case the codeblock given as argument will be	547	C<Guard::guard> function instead.
498	executed. This is useful to free locks or other resources in case of a
499	runtime error or when the coroutine gets canceled, as in both cases the
500	guard block will be executed. The guard object supports only one method,
501	C<< ->cancel >>, which will keep the codeblock from being executed.
502		548
503	Example: set some flag and clear it again when the coroutine gets canceled
504	or the function returns:
505
506	sub do_something {
507	my $guard = Coro::guard { $busy = 0 };
508	$busy = 1;
509
510	# do something that requires $busy to be true
511	}
512
513	=cut	549	=cut
514		550
515	sub guard(&) {	551	BEGIN { *guard = \&Guard::guard }
516	bless \(my $cb = $_[0]), "Coro::guard"
517	}
518
519	sub Coro::guard::cancel {
520	${$_[0]} = sub { };
521	}
522
523	sub Coro::guard::DESTROY {
524	${$_[0]}->();
525	}
526
527		552
528	=item unblock_sub { ... }	553	=item unblock_sub { ... }
529		554
530	This utility function takes a BLOCK or code reference and "unblocks" it,	555	This utility function takes a BLOCK or code reference and "unblocks" it,
531	returning the new coderef. This means that the new coderef will return	556	returning a new coderef. Unblocking means that calling the new coderef
532	immediately without blocking, returning nothing, while the original code	557	will return immediately without blocking, returning nothing, while the
533	ref will be called (with parameters) from within its own coroutine.	558	original code ref will be called (with parameters) from within another
		559	coroutine.
534		560
535	The reason this function exists is that many event libraries (such as the	561	The reason this function exists is that many event libraries (such as the
536	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	562	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
537	of thread-safety). This means you must not block within event callbacks,	563	of reentrancy). This means you must not block within event callbacks,
538	otherwise you might suffer from crashes or worse.	564	otherwise you might suffer from crashes or worse. The only event library
		565	currently known that is safe to use without C<unblock_sub> is L<EV>.
539		566
540	This function allows your callbacks to block by executing them in another	567	This function allows your callbacks to block by executing them in another
541	coroutine where it is safe to block. One example where blocking is handy	568	coroutine where it is safe to block. One example where blocking is handy
542	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	569	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
543	disk.	570	disk, for example.
544		571
545	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	572	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
546	creating event callbacks that want to block.	573	creating event callbacks that want to block.
		574
		575	If your handler does not plan to block (e.g. simply sends a message to
		576	another coroutine, or puts some other coroutine into the ready queue),
		577	there is no reason to use C<unblock_sub>.
		578
		579	Note that you also need to use C<unblock_sub> for any other callbacks that
		580	are indirectly executed by any C-based event loop. For example, when you
		581	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		582	provides callbacks that are the result of some event callback, then you
		583	must not block either, or use C<unblock_sub>.
547		584
548	=cut	585	=cut
549		586
550	our @unblock_queue;	587	our @unblock_queue;
551		588
…		…
554	# return immediately and can be reused) and because we cannot cede	591	# return immediately and can be reused) and because we cannot cede
555	# inside an event callback.	592	# inside an event callback.
556	our $unblock_scheduler = new Coro sub {	593	our $unblock_scheduler = new Coro sub {
557	while () {	594	while () {
558	while (my $cb = pop @unblock_queue) {	595	while (my $cb = pop @unblock_queue) {
559	# this is an inlined copy of async_pool	596	&async_pool (@$cb);
560	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
561		597
562	$coro->{_invoke} = $cb;
563	$coro->ready;
564	cede; # for short-lived callbacks, this reduces pressure on the coro pool	598	# for short-lived callbacks, this reduces pressure on the coro pool
		599	# as the chance is very high that the async_poll coro will be back
		600	# in the idle state when cede returns
		601	cede;
565	}	602	}
566	schedule; # sleep well	603	schedule; # sleep well
567	}	604	}
568	};	605	};
569	$unblock_scheduler->desc ("[unblock_sub scheduler]");	606	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
570		607
571	sub unblock_sub(&) {	608	sub unblock_sub(&) {
572	my $cb = shift;	609	my $cb = shift;
573		610
574	sub {	611	sub {
575	unshift @unblock_queue, [$cb, @_];	612	unshift @unblock_queue, [$cb, @_];
576	$unblock_scheduler->ready;	613	$unblock_scheduler->ready;
577	}	614	}
578	}	615	}
579		616
		617	=item $cb = Coro::rouse_cb
		618
		619	Create and return a "rouse callback". That's a code reference that,
		620	when called, will remember a copy of its arguments and notify the owner
		621	coroutine of the callback.
		622
		623	See the next function.
		624
		625	=item @args = Coro::rouse_wait [$cb]
		626
		627	Wait for the specified rouse callback (or the last one that was created in
		628	this coroutine).
		629
		630	As soon as the callback is invoked (or when the callback was invoked
		631	before C<rouse_wait>), it will return the arguments originally passed to
		632	the rouse callback.
		633
		634	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		635
580	=back	636	=back
581		637
582	=cut	638	=cut
583		639
584	1;	640	1;
585		641
		642	=head1 HOW TO WAIT FOR A CALLBACK
		643
		644	It is very common for a coroutine to wait for some callback to be
		645	called. This occurs naturally when you use coroutines in an otherwise
		646	event-based program, or when you use event-based libraries.
		647
		648	These typically register a callback for some event, and call that callback
		649	when the event occured. In a coroutine, however, you typically want to
		650	just wait for the event, simplyifying things.
		651
		652	For example C<< AnyEvent->child >> registers a callback to be called when
		653	a specific child has exited:
		654
		655	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		656
		657	But from withina coroutine, you often just want to write this:
		658
		659	my $status = wait_for_child $pid;
		660
		661	Coro offers two functions specifically designed to make this easy,
		662	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		663
		664	The first function, C<rouse_cb>, generates and returns a callback that,
		665	when invoked, will save its arguments and notify the coroutine that
		666	created the callback.
		667
		668	The second function, C<rouse_wait>, waits for the callback to be called
		669	(by calling C<schedule> to go to sleep) and returns the arguments
		670	originally passed to the callback.
		671
		672	Using these functions, it becomes easy to write the C<wait_for_child>
		673	function mentioned above:
		674
		675	sub wait_for_child($) {
		676	my ($pid) = @_;
		677
		678	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		679
		680	my ($rpid, $rstatus) = Coro::rouse_wait;
		681	$rstatus
		682	}
		683
		684	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		685	you can roll your own, using C<schedule>:
		686
		687	sub wait_for_child($) {
		688	my ($pid) = @_;
		689
		690	# store the current coroutine in $current,
		691	# and provide result variables for the closure passed to ->child
		692	my $current = $Coro::current;
		693	my ($done, $rstatus);
		694
		695	# pass a closure to ->child
		696	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		697	$rstatus = $_[1]; # remember rstatus
		698	$done = 1; # mark $rstatus as valud
		699	});
		700
		701	# wait until the closure has been called
		702	schedule while !$done;
		703
		704	$rstatus
		705	}
		706
		707
586	=head1 BUGS/LIMITATIONS	708	=head1 BUGS/LIMITATIONS
587		709
588	- you must make very sure that no coro is still active on global	710	=over 4
589	destruction. very bad things might happen otherwise (usually segfaults).
590		711
		712	=item fork with pthread backend
		713
		714	When Coro is compiled using the pthread backend (which isn't recommended
		715	but required on many BSDs as their libcs are completely broken), then
		716	coroutines will not survive a fork. There is no known workaround except to
		717	fix your libc and use a saner backend.
		718
		719	=item perl process emulation ("threads")
		720
591	- this module is not thread-safe. You should only ever use this module	721	This module is not perl-pseudo-thread-safe. You should only ever use this
592	from the same thread (this requirement might be loosened in the future	722	module from the first thread (this requirement might be removed in the
593	to allow per-thread schedulers, but Coro::State does not yet allow	723	future to allow per-thread schedulers, but Coro::State does not yet allow
594	this).	724	this). I recommend disabling thread support and using processes, as having
		725	the windows process emulation enabled under unix roughly halves perl
		726	performance, even when not used.
		727
		728	=item coroutine switching not signal safe
		729
		730	You must not switch to another coroutine from within a signal handler
		731	(only relevant with %SIG - most event libraries provide safe signals).
		732
		733	That means you I<MUST NOT> call any function that might "block" the
		734	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		735	anything that calls those. Everything else, including calling C<ready>,
		736	works.
		737
		738	=back
		739
595		740
596	=head1 SEE ALSO	741	=head1 SEE ALSO
597		742
		743	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		744
		745	Debugging: L<Coro::Debug>.
		746
598	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	747	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
599		748
600	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	749	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		750	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
601		751
602	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	752	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
603		753
604	Embedding: L<Coro:MakeMaker>	754	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		755	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		756	L<Coro::Select>.
		757
		758	XS API: L<Coro::MakeMaker>.
		759
		760	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
605		761
606	=head1 AUTHOR	762	=head1 AUTHOR
607		763
608	Marc Lehmann <schmorp@schmorp.de>	764	Marc Lehmann <schmorp@schmorp.de>
609	http://home.schmorp.de/	765	http://home.schmorp.de/

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Revision 1.245 by root, Sun Dec 14 19:52:58 2008 UTC