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

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.104 by root, Thu Jan 4 23:49:27 2007 UTC vs.
Revision 1.226 by root, Wed Nov 19 16:01:32 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 $VERSION = 5.0;
56		73
57	our @EXPORT = qw(async cede schedule terminate current unblock_sub);	74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
58	our %EXPORT_TAGS = (	75	our %EXPORT_TAGS = (
59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60	);	77	);
61	our @EXPORT_OK = (@{$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
…		…
203	my $coro = new Coro @_;	205	my $coro = new Coro @_;
204	$coro->ready;	206	$coro->ready;
205	$coro	207	$coro
206	}	208	}
207		209
		210	=item async_pool { ... } [@args...]
		211
		212	Similar to C<async>, but uses a coroutine pool, so you should not call
		213	terminate or join on it (although you are allowed to), and you get a
		214	coroutine that might have executed other code already (which can be good
		215	or bad :).
		216
		217	On the plus side, this function is faster than creating (and destroying)
		218	a completly new coroutine, so if you need a lot of generic coroutines in
		219	quick successsion, use C<async_pool>, not C<async>.
		220
		221	The code block is executed in an C<eval> context and a warning will be
		222	issued in case of an exception instead of terminating the program, as
		223	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		224	will not work in the expected way, unless you call terminate or cancel,
		225	which somehow defeats the purpose of pooling (but is fine in the
		226	exceptional case).
		227
		228	The priority will be reset to C<0> after each run, tracing will be
		229	disabled, the description will be reset and the default output filehandle
		230	gets restored, so you can change all these. Otherwise the coroutine will
		231	be re-used "as-is": most notably if you change other per-coroutine global
		232	stuff such as C<$/> you I<must needs> revert that change, which is most
		233	simply done by using local as in: C<< local $/ >>.
		234
		235	The idle pool size is limited to C<8> idle coroutines (this can be
		236	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		237	coros as required.
		238
		239	If you are concerned about pooled coroutines growing a lot because a
		240	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		241	{ terminate }> once per second or so to slowly replenish the pool. In
		242	addition to that, when the stacks used by a handler grows larger than 16kb
		243	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		244
		245	=cut
		246
		247	our $POOL_SIZE = 8;
		248	our $POOL_RSS = 16 * 1024;
		249	our @async_pool;
		250
		251	sub pool_handler {
		252	my $cb;
		253
		254	while () {
		255	eval {
		256	while () {
		257	_pool_1 $cb;
		258	&$cb;
		259	_pool_2 $cb;
		260	&schedule;
		261	}
		262	};
		263
		264	if ($@) {
		265	last if $@ eq "\3async_pool terminate\2\n";
		266	warn $@;
		267	}
		268	}
		269	}
		270
		271	sub async_pool(&@) {
		272	# this is also inlined into the unblock_scheduler
		273	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		274
		275	$coro->{_invoke} = [@_];
		276	$coro->ready;
		277
		278	$coro
		279	}
		280
		281	=back
		282
		283	=head2 STATIC METHODS
		284
		285	Static methods are actually functions that operate on the current coroutine.
		286
		287	=over 4
		288
208	=item schedule	289	=item schedule
209		290
210	Calls the scheduler. Please note that the current coroutine will not be put	291	Calls the scheduler. The scheduler will find the next coroutine that is
		292	to be run from the ready queue and switches to it. The next coroutine
		293	to be run is simply the one with the highest priority that is longest
		294	in its ready queue. If there is no coroutine ready, it will clal the
		295	C<$Coro::idle> hook.
		296
		297	Please note that the current coroutine will I<not> be put into the ready
211	into the ready queue, so calling this function usually means you will	298	queue, so calling this function usually means you will never be called
212	never be called again unless something else (e.g. an event handler) calls	299	again unless something else (e.g. an event handler) calls C<< ->ready >>,
213	ready.	300	thus waking you up.
214		301
215	The canonical way to wait on external events is this:	302	This makes C<schedule> I<the> generic method to use to block the current
		303	coroutine and wait for events: first you remember the current coroutine in
		304	a variable, then arrange for some callback of yours to call C<< ->ready
		305	>> on that once some event happens, and last you call C<schedule> to put
		306	yourself to sleep. Note that a lot of things can wake your coroutine up,
		307	so you need to check whether the event indeed happened, e.g. by storing the
		308	status in a variable.
216		309
		310	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
		311
		312	=item cede
		313
		314	"Cede" to other coroutines. This function puts the current coroutine into
		315	the ready queue and calls C<schedule>, which has the effect of giving
		316	up the current "timeslice" to other coroutines of the same or higher
		317	priority. Once your coroutine gets its turn again it will automatically be
		318	resumed.
		319
		320	This function is often called C<yield> in other languages.
		321
		322	=item Coro::cede_notself
		323
		324	Works like cede, but is not exported by default and will cede to I<any>
		325	coroutine, regardless of priority. This is useful sometimes to ensure
		326	progress is made.
		327
		328	=item terminate [arg...]
		329
		330	Terminates the current coroutine with the given status values (see L<cancel>).
		331
		332	=item killall
		333
		334	Kills/terminates/cancels all coroutines except the currently running
		335	one. This is useful after a fork, either in the child or the parent, as
		336	usually only one of them should inherit the running coroutines.
		337
		338	Note that while this will try to free some of the main programs resources,
		339	you cannot free all of them, so if a coroutine that is not the main
		340	program calls this function, there will be some one-time resource leak.
		341
		342	=cut
		343
		344	sub terminate {
		345	$current->{_status} = [@_];
		346	push @destroy, $current;
		347	$manager->ready;
		348	do { &schedule } while 1;
		349	}
		350
		351	sub killall {
		352	for (Coro::State::list) {
		353	$_->cancel
		354	if $_ != $current && UNIVERSAL::isa $_, "Coro";
217	{	355	}
218	# remember current coroutine	356	}
		357
		358	=back
		359
		360	=head2 COROUTINE METHODS
		361
		362	These are the methods you can call on coroutine objects (or to create
		363	them).
		364
		365	=over 4
		366
		367	=item new Coro \&sub [, @args...]
		368
		369	Create a new coroutine and return it. When the sub returns, the coroutine
		370	automatically terminates as if C<terminate> with the returned values were
		371	called. To make the coroutine run you must first put it into the ready
		372	queue by calling the ready method.
		373
		374	See C<async> and C<Coro::State::new> for additional info about the
		375	coroutine environment.
		376
		377	=cut
		378
		379	sub _terminate {
		380	terminate &{+shift};
		381	}
		382
		383	=item $success = $coroutine->ready
		384
		385	Put the given coroutine into the end of its ready queue (there is one
		386	queue for each priority) and return true. If the coroutine is already in
		387	the ready queue, do nothing and return false.
		388
		389	This ensures that the scheduler will resume this coroutine automatically
		390	once all the coroutines of higher priority and all coroutines of the same
		391	priority that were put into the ready queue earlier have been resumed.
		392
		393	=item $is_ready = $coroutine->is_ready
		394
		395	Return whether the coroutine is currently the ready queue or not,
		396
		397	=item $coroutine->cancel (arg...)
		398
		399	Terminates the given coroutine and makes it return the given arguments as
		400	status (default: the empty list). Never returns if the coroutine is the
		401	current coroutine.
		402
		403	=cut
		404
		405	sub cancel {
		406	my $self = shift;
		407
		408	if ($current == $self) {
		409	terminate @_;
		410	} else {
		411	$self->{_status} = [@_];
		412	$self->_cancel;
		413	}
		414	}
		415
		416	=item $coroutine->throw ([$scalar])
		417
		418	If C<$throw> is specified and defined, it will be thrown as an exception
		419	inside the coroutine at the next convenient point in time. Otherwise
		420	clears the exception object.
		421
		422	Coro will check for the exception each time a schedule-like-function
		423	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		424	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		425	detect this case and return early in case an exception is pending.
		426
		427	The exception object will be thrown "as is" with the specified scalar in
		428	C<$@>, i.e. if it is a string, no line number or newline will be appended
		429	(unlike with C<die>).
		430
		431	This can be used as a softer means than C<cancel> to ask a coroutine to
		432	end itself, although there is no guarantee that the exception will lead to
		433	termination, and if the exception isn't caught it might well end the whole
		434	program.
		435
		436	You might also think of C<throw> as being the moral equivalent of
		437	C<kill>ing a coroutine with a signal (in this case, a scalar).
		438
		439	=item $coroutine->join
		440
		441	Wait until the coroutine terminates and return any values given to the
		442	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		443	from multiple coroutines, and all will be resumed and given the status
		444	return once the C<$coroutine> terminates.
		445
		446	=cut
		447
		448	sub join {
		449	my $self = shift;
		450
		451	unless ($self->{_status}) {
219	my $current = $Coro::current;	452	my $current = $current;
220		453
221	# register a hypothetical event handler	454	push @{$self->{_on_destroy}}, sub {
222	on_event_invoke sub {
223	# wake up sleeping coroutine
224	$current->ready;	455	$current->ready;
225	undef $current;	456	undef $current;
226	};	457	};
227		458
228	# call schedule until event occured.
229	# in case we are woken up for other reasons
230	# (current still defined), loop.
231	Coro::schedule while $current;
232	}
233
234	=item cede
235
236	"Cede" to other coroutines. This function puts the current coroutine into the
237	ready queue and calls C<schedule>, which has the effect of giving up the
238	current "timeslice" to other coroutines of the same or higher priority.
239
240	=item Coro::cede_notself
241
242	Works like cede, but is not exported by default and will cede to any
243	coroutine, regardless of priority, once.
244
245	=item terminate [arg...]
246
247	Terminates the current coroutine with the given status values (see L<cancel>).
248
249	=cut
250
251	sub terminate {
252	$current->cancel (@_);
253	}
254
255	=back
256
257	# dynamic methods
258
259	=head2 COROUTINE METHODS
260
261	These are the methods you can call on coroutine objects.
262
263	=over 4
264
265	=item new Coro \&sub [, @args...]
266
267	Create a new coroutine and return it. When the sub returns the coroutine
268	automatically terminates as if C<terminate> with the returned values were
269	called. To make the coroutine run you must first put it into the ready queue
270	by calling the ready method.
271
272	Calling C<exit> in a coroutine will not work correctly, so do not do that.
273
274	=cut
275
276	sub _run_coro {
277	terminate &{+shift};
278	}
279
280	sub new {
281	my $class = shift;
282
283	$class->SUPER::new (\&_run_coro, @_)
284	}
285
286	=item $success = $coroutine->ready
287
288	Put the given coroutine into the ready queue (according to it's priority)
289	and return true. If the coroutine is already in the ready queue, do nothing
290	and return false.
291
292	=item $is_ready = $coroutine->is_ready
293
294	Return wether the coroutine is currently the ready queue or not,
295
296	=item $coroutine->cancel (arg...)
297
298	Terminates the given coroutine and makes it return the given arguments as
299	status (default: the empty list). Never returns if the coroutine is the
300	current coroutine.
301
302	=cut
303
304	sub cancel {
305	my $self = shift;
306	$self->{status} = [@_];
307
308	if ($current == $self) {
309	push @destroy, $self;
310	$manager->ready;
311	&schedule while 1;
312	} else {
313	$self->_cancel;
314	}
315	}
316
317	=item $coroutine->join
318
319	Wait until the coroutine terminates and return any values given to the
320	C<terminate> or C<cancel> functions. C<join> can be called multiple times
321	from multiple coroutine.
322
323	=cut
324
325	sub join {
326	my $self = shift;
327
328	unless ($self->{status}) {
329	my $current = $current;
330
331	push @{$self->{destroy_cb}}, sub {
332	$current->ready;
333	undef $current;
334	};
335
336	&schedule while $current;	459	&schedule while $current;
337	}	460	}
338		461
339	wantarray ? @{$self->{status}} : $self->{status}[0];	462	wantarray ? @{$self->{_status}} : $self->{_status}[0];
340	}	463	}
341		464
342	=item $coroutine->on_destroy (\&cb)	465	=item $coroutine->on_destroy (\&cb)
343		466
344	Registers a callback that is called when this coroutine gets destroyed,	467	Registers a callback that is called when this coroutine gets destroyed,
345	but before it is joined. The callback gets passed the terminate arguments,	468	but before it is joined. The callback gets passed the terminate arguments,
346	if any.	469	if any, and I<must not> die, under any circumstances.
347		470
348	=cut	471	=cut
349		472
350	sub on_destroy {	473	sub on_destroy {
351	my ($self, $cb) = @_;	474	my ($self, $cb) = @_;
352		475
353	push @{ $self->{destroy_cb} }, $cb;	476	push @{ $self->{_on_destroy} }, $cb;
354	}	477	}
355		478
356	=item $oldprio = $coroutine->prio ($newprio)	479	=item $oldprio = $coroutine->prio ($newprio)
357		480
358	Sets (or gets, if the argument is missing) the priority of the	481	Sets (or gets, if the argument is missing) the priority of the
…		…
381	higher values mean lower priority, just as in unix).	504	higher values mean lower priority, just as in unix).
382		505
383	=item $olddesc = $coroutine->desc ($newdesc)	506	=item $olddesc = $coroutine->desc ($newdesc)
384		507
385	Sets (or gets in case the argument is missing) the description for this	508	Sets (or gets in case the argument is missing) the description for this
386	coroutine. This is just a free-form string you can associate with a coroutine.	509	coroutine. This is just a free-form string you can associate with a
		510	coroutine.
		511
		512	This method simply sets the C<< $coroutine->{desc} >> member to the given
		513	string. You can modify this member directly if you wish.
387		514
388	=cut	515	=cut
389		516
390	sub desc {	517	sub desc {
391	my $old = $_[0]{desc};	518	my $old = $_[0]{desc};
…		…
400	=over 4	527	=over 4
401		528
402	=item Coro::nready	529	=item Coro::nready
403		530
404	Returns the number of coroutines that are currently in the ready state,	531	Returns the number of coroutines that are currently in the ready state,
405	i.e. that can be swicthed to. The value C<0> means that the only runnable	532	i.e. that can be switched to by calling C<schedule> directory or
		533	indirectly. The value C<0> means that the only runnable coroutine is the
406	coroutine is the currently running one, so C<cede> would have no effect,	534	currently running one, so C<cede> would have no effect, and C<schedule>
407	and C<schedule> would cause a deadlock unless there is an idle handler	535	would cause a deadlock unless there is an idle handler that wakes up some
408	that wakes up some coroutines.	536	coroutines.
409		537
410	=item my $guard = Coro::guard { ... }	538	=item my $guard = Coro::guard { ... }
411		539
412	This creates and returns a guard object. Nothing happens until the objetc	540	This creates and returns a guard object. Nothing happens until the object
413	gets destroyed, in which case the codeblock given as argument will be	541	gets destroyed, in which case the codeblock given as argument will be
414	executed. This is useful to free locks or other resources in case of a	542	executed. This is useful to free locks or other resources in case of a
415	runtime error or when the coroutine gets canceled, as in both cases the	543	runtime error or when the coroutine gets canceled, as in both cases the
416	guard block will be executed. The guard object supports only one method,	544	guard block will be executed. The guard object supports only one method,
417	C<< ->cancel >>, which will keep the codeblock from being executed.	545	C<< ->cancel >>, which will keep the codeblock from being executed.
…		…
442		570
443		571
444	=item unblock_sub { ... }	572	=item unblock_sub { ... }
445		573
446	This utility function takes a BLOCK or code reference and "unblocks" it,	574	This utility function takes a BLOCK or code reference and "unblocks" it,
447	returning the new coderef. This means that the new coderef will return	575	returning a new coderef. Unblocking means that calling the new coderef
448	immediately without blocking, returning nothing, while the original code	576	will return immediately without blocking, returning nothing, while the
449	ref will be called (with parameters) from within its own coroutine.	577	original code ref will be called (with parameters) from within another
		578	coroutine.
450		579
451	The reason this fucntion exists is that many event libraries (such as the	580	The reason this function exists is that many event libraries (such as the
452	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	581	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
453	of thread-safety). This means you must not block within event callbacks,	582	of thread-safety). This means you must not block within event callbacks,
454	otherwise you might suffer from crashes or worse.	583	otherwise you might suffer from crashes or worse. The only event library
		584	currently known that is safe to use without C<unblock_sub> is L<EV>.
455		585
456	This function allows your callbacks to block by executing them in another	586	This function allows your callbacks to block by executing them in another
457	coroutine where it is safe to block. One example where blocking is handy	587	coroutine where it is safe to block. One example where blocking is handy
458	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	588	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
459	disk.	589	disk, for example.
460		590
461	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	591	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
462	creating event callbacks that want to block.	592	creating event callbacks that want to block.
463		593
464	=cut	594	If your handler does not plan to block (e.g. simply sends a message to
		595	another coroutine, or puts some other coroutine into the ready queue),
		596	there is no reason to use C<unblock_sub>.
465		597
466	our @unblock_pool;	598	Note that you also need to use C<unblock_sub> for any other callbacks that
		599	are indirectly executed by any C-based event loop. For example, when you
		600	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		601	provides callbacks that are the result of some event callback, then you
		602	must not block either, or use C<unblock_sub>.
		603
		604	=cut
		605
467	our @unblock_queue;	606	our @unblock_queue;
468	our $UNBLOCK_POOL_SIZE = 2;
469		607
470	sub unblock_handler_ {	608	# we create a special coro because we want to cede,
471	while () {	609	# to reduce pressure on the coro pool (because most callbacks
472	my ($cb, @arg) = @{ delete $Coro::current->{arg} };	610	# return immediately and can be reused) and because we cannot cede
473	$cb->(@arg);	611	# inside an event callback.
474
475	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
476	push @unblock_pool, $Coro::current;
477	schedule;
478	}
479	}
480
481	our $unblock_scheduler = async {	612	our $unblock_scheduler = new Coro sub {
482	while () {	613	while () {
483	while (my $cb = pop @unblock_queue) {	614	while (my $cb = pop @unblock_queue) {
484	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);	615	# this is an inlined copy of async_pool
485	$handler->{arg} = $cb;	616	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		617
		618	$coro->{_invoke} = $cb;
486	$handler->ready;	619	$coro->ready;
487	cede;	620	cede; # for short-lived callbacks, this reduces pressure on the coro pool
488	}	621	}
489		622	schedule; # sleep well
490	schedule;
491	}	623	}
492	};	624	};
		625	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
493		626
494	sub unblock_sub(&) {	627	sub unblock_sub(&) {
495	my $cb = shift;	628	my $cb = shift;
496		629
497	sub {	630	sub {
498	push @unblock_queue, [$cb, @_];	631	unshift @unblock_queue, [$cb, @_];
499	$unblock_scheduler->ready;	632	$unblock_scheduler->ready;
500	}	633	}
501	}	634	}
502		635
		636	=item $cb = Coro::rouse_cb
		637
		638	Create and return a "rouse callback". That's a code reference that, when
		639	called, will save its arguments and notify the owner coroutine of the
		640	callback.
		641
		642	See the next function.
		643
		644	=item @args = Coro::rouse_wait [$cb]
		645
		646	Wait for the specified rouse callback (or the last one tht was created in
		647	this coroutine).
		648
		649	As soon as the callback is invoked (or when the calback was invoked before
		650	C<rouse_wait>), it will return a copy of the arguments originally passed
		651	to the rouse callback.
		652
		653	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		654
503	=back	655	=back
504		656
505	=cut	657	=cut
506		658
507	1;	659	1;
508		660
		661	=head1 HOW TO WAIT FOR A CALLBACK
		662
		663	It is very common for a coroutine to wait for some callback to be
		664	called. This occurs naturally when you use coroutines in an otherwise
		665	event-based program, or when you use event-based libraries.
		666
		667	These typically register a callback for some event, and call that callback
		668	when the event occured. In a coroutine, however, you typically want to
		669	just wait for the event, simplyifying things.
		670
		671	For example C<< AnyEvent->child >> registers a callback to be called when
		672	a specific child has exited:
		673
		674	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		675
		676	But from withina coroutine, you often just want to write this:
		677
		678	my $status = wait_for_child $pid;
		679
		680	Coro offers two functions specifically designed to make this easy,
		681	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		682
		683	The first function, C<rouse_cb>, generates and returns a callback that,
		684	when invoked, will save it's arguments and notify the coroutine that
		685	created the callback.
		686
		687	The second function, C<rouse_wait>, waits for the callback to be called
		688	(by calling C<schedule> to go to sleep) and returns the arguments
		689	originally passed to the callback.
		690
		691	Using these functions, it becomes easy to write the C<wait_for_child>
		692	function mentioned above:
		693
		694	sub wait_for_child($) {
		695	my ($pid) = @_;
		696
		697	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		698
		699	my ($rpid, $rstatus) = Coro::rouse_wait;
		700	$rstatus
		701	}
		702
		703	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		704	you can roll your own, using C<schedule>:
		705
		706	sub wait_for_child($) {
		707	my ($pid) = @_;
		708
		709	# store the current coroutine in $current,
		710	# and provide result variables for the closure passed to ->child
		711	my $current = $Coro::current;
		712	my ($done, $rstatus);
		713
		714	# pass a closure to ->child
		715	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		716	$rstatus = $_[1]; # remember rstatus
		717	$done = 1; # mark $rstatus as valud
		718	});
		719
		720	# wait until the closure has been called
		721	schedule while !$done;
		722
		723	$rstatus
		724	}
		725
		726
509	=head1 BUGS/LIMITATIONS	727	=head1 BUGS/LIMITATIONS
510		728
511	- you must make very sure that no coro is still active on global	729	=over 4
512	destruction. very bad things might happen otherwise (usually segfaults).
513		730
		731	=item fork with pthread backend
		732
		733	When Coro is compiled using the pthread backend (which isn't recommended
		734	but required on many BSDs as their libcs are completely broken), then
		735	coroutines will not survive a fork. There is no known workaround except to
		736	fix your libc and use a saner backend.
		737
		738	=item perl process emulation ("threads")
		739
514	- this module is not thread-safe. You should only ever use this module	740	This module is not perl-pseudo-thread-safe. You should only ever use this
515	from the same thread (this requirement might be losened in the future	741	module from the same thread (this requirement might be removed in the
516	to allow per-thread schedulers, but Coro::State does not yet allow	742	future to allow per-thread schedulers, but Coro::State does not yet allow
517	this).	743	this). I recommend disabling thread support and using processes, as having
		744	the windows process emulation enabled under unix roughly halves perl
		745	performance, even when not used.
		746
		747	=item coroutine switching not signal safe
		748
		749	You must not switch to another coroutine from within a signal handler
		750	(only relevant with %SIG - most event libraries provide safe signals).
		751
		752	That means you I<MUST NOT> call any function that might "block" the
		753	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		754	anything that calls those. Everything else, including calling C<ready>,
		755	works.
		756
		757	=back
		758
518		759
519	=head1 SEE ALSO	760	=head1 SEE ALSO
520		761
		762	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		763
		764	Debugging: L<Coro::Debug>.
		765
521	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	766	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
522		767
523	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	768	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
524		769
525	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	770	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
526		771
527	Embedding: L<Coro:MakeMaker>	772	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		773
		774	XS API: L<Coro::MakeMaker>.
		775
		776	Low level Configuration, Coroutine Environment: L<Coro::State>.
528		777
529	=head1 AUTHOR	778	=head1 AUTHOR
530		779
531	Marc Lehmann <schmorp@schmorp.de>	780	Marc Lehmann <schmorp@schmorp.de>
532	http://home.schmorp.de/	781	http://home.schmorp.de/

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Comparing cvsroot/Coro/Coro.pm (file contents): Revision 1.104 by root, Thu Jan 4 23:49:27 2007 UTC vs. Revision 1.226 by root, Wed Nov 19 16:01:32 2008 UTC

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Revision 1.226 by root, Wed Nov 19 16:01:32 2008 UTC