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

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.93 by root, Fri Dec 1 19:41:06 2006 UTC vs.
Revision 1.224 by root, Wed Nov 19 05:52:42 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 to	31	This module collection manages coroutines. Coroutines are similar to
24	threads but don't run in parallel.	32	threads but don't (in general) run in parallel at the same time even
		33	on SMP machines. The specific flavor of coroutine used in this module
		34	also guarantees you that it will not switch between coroutines unless
		35	necessary, at easily-identified points in your program, so locking and
		36	parallel access are rarely an issue, making coroutine programming much
		37	safer and easier than threads programming.
25		38
		39	Unlike a normal perl program, however, coroutines allow you to have
		40	multiple running interpreters that share data, which is especially useful
		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).
		51
26	In this module, coroutines are defined as "callchain + lexical variables	52	In this module, coroutines are defined as "callchain + lexical variables +
27	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own	53	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
28	callchain, it's own set of lexicals and it's own set of perl's most	54	its own set of lexicals and its own set of perls most important global
29	important global variables.	55	variables (see L<Coro::State> for more configuration).
30		56
31	=cut	57	=cut
32		58
33	package Coro;	59	package Coro;
34		60
35	use strict;	61	use strict qw(vars subs);
36	no warnings "uninitialized";	62	no warnings "uninitialized";
37		63
38	use Coro::State;	64	use Coro::State;
39		65
40	use base qw(Coro::State Exporter);	66	use base qw(Coro::State Exporter);
41		67
42	our $idle; # idle handler	68	our $idle; # idle handler
43	our $main; # main coroutine	69	our $main; # main coroutine
44	our $current; # current coroutine	70	our $current; # current coroutine
45		71
46	our $VERSION = '3.0';	72	our $VERSION = 5.0;
47		73
48	our @EXPORT = qw(async cede schedule terminate current unblock_sub);	74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
49	our %EXPORT_TAGS = (	75	our %EXPORT_TAGS = (
50	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51	);	77	);
52	our @EXPORT_OK = @{$EXPORT_TAGS{prio}};	78	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
53
54	{
55	my @async;
56	my $init;
57
58	# this way of handling attributes simply is NOT scalable ;()
59	sub import {
60	no strict 'refs';
61
62	Coro->export_to_level (1, @_);
63
64	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
65	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
66	my ($package, $ref) = (shift, shift);
67	my @attrs;
68	for (@_) {
69	if ($_ eq "Coro") {
70	push @async, $ref;
71	unless ($init++) {
72	eval q{
73	sub INIT {
74	&async(pop @async) while @async;
75	}
76	};
77	}
78	} else {
79	push @attrs, $_;
80	}
81	}
82	return $old ? $old->($package, $ref, @attrs) : @attrs;
83	};
84	}
85
86	}
87		79
88	=over 4	80	=over 4
89		81
90	=item $main	82	=item $Coro::main
91		83
92	This coroutine represents the main program.	84	This variable stores the coroutine object that represents the main
		85	program. While you cna C<ready> it and do most other things you can do to
		86	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		87	whether you are running in the main program or not.
93		88
94	=cut	89	=cut
95		90
96	$main = new Coro;	91	# $main is now being initialised by Coro::State
97		92
98	=item $current (or as function: current)	93	=item $Coro::current
99		94
100	The current coroutine (the last coroutine switched to). The initial value	95	The coroutine object representing the current coroutine (the last
		96	coroutine that the Coro scheduler switched to). The initial value is
101	is C<$main> (of course).	97	C<$Coro::main> (of course).
102		98
103	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
104	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
105	C<Coro::current> function instead.	101	not otherwise modify the variable itself.
106		102
107	=cut	103	=cut
108		104
109	# maybe some other module used Coro::Specific before...
110	$main->{specific} = $current->{specific}
111	if $current;
112
113	_set_current $main;
114
115	sub current() { $current }	105	sub current() { $current } # [DEPRECATED]
116		106
117	=item $idle	107	=item $Coro::idle
118		108
119	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
120	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
121	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.
122		117
123	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
124	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
125	coroutine so the scheduler can run it.	120	coroutine so the scheduler can run it.
126		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
127	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
128	handlers), then it must be prepared to be called recursively.	131	handlers), then it must be prepared to be called recursively itself.
129		132
130	=cut	133	=cut
131		134
132	$idle = sub {	135	$idle = sub {
133	print STDERR "FATAL: deadlock detected\n";	136	require Carp;
134	exit (51);	137	Carp::croak ("FATAL: deadlock detected");
135	};	138	};
		139
		140	sub _cancel {
		141	my ($self) = @_;
		142
		143	# free coroutine data and mark as destructed
		144	$self->_destroy
		145	or return;
		146
		147	# call all destruction callbacks
		148	$_->(@{$self->{_status}})
		149	for @{ delete $self->{_on_destroy} \|\| [] };
		150	}
136		151
137	# this coroutine is necessary because a coroutine	152	# this coroutine is necessary because a coroutine
138	# cannot destroy itself.	153	# cannot destroy itself.
139	my @destroy;	154	my @destroy;
		155	my $manager;
		156
140	my $manager; $manager = new Coro sub {	157	$manager = new Coro sub {
141	while () {	158	while () {
142	# by overwriting the state object with the manager we destroy it	159	(shift @destroy)->_cancel
143	# while still being able to schedule this coroutine (in case it has
144	# been readied multiple times. this is harmless since the manager
145	# can be called as many times as neccessary and will always
146	# remove itself from the runqueue
147	while (@destroy) {	160	while @destroy;
148	my $coro = pop @destroy;
149	$coro->{status} \|\|= [];
150	$_->ready for @{delete $coro->{join} \|\| []};
151		161
152	# the next line destroys the coro state, but keeps the
153	# coroutine itself intact (we basically make it a zombie
154	# coroutine that always runs the manager thread, so it's possible
155	# to transfer() to this coroutine).
156	$coro->_clone_state_from ($manager);
157	}
158	&schedule;	162	&schedule;
159	}	163	}
160	};	164	};
161		165	$manager->{desc} = "[coro manager]";
162	# static methods. not really.	166	$manager->prio (PRIO_MAX);
163		167
164	=back	168	=back
165		169
166	=head2 STATIC METHODS	170	=head2 SIMPLE COROUTINE CREATION
167
168	Static methods are actually functions that operate on the current coroutine only.
169		171
170	=over 4	172	=over 4
171		173
172	=item async { ... } [@args...]	174	=item async { ... } [@args...]
173		175
174	Create a new asynchronous coroutine and return it's coroutine object	176	Create a new coroutine and return it's coroutine object (usually
175	(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
176	terminated.	182	terminated.
177		183
178	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.
179		185
180	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
181	program.	187	environment in which coroutines are executed.
182		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
183	# create a new coroutine that just prints its arguments	196	Example: Create a new coroutine that just prints its arguments.
		197
184	async {	198	async {
185	print "@_\n";	199	print "@_\n";
186	} 1,2,3,4;	200	} 1,2,3,4;
187		201
188	=cut	202	=cut
189		203
190	sub async(&@) {	204	sub async(&@) {
191	my $pid = new Coro @_;	205	my $coro = new Coro @_;
192	$pid->ready;	206	$coro->ready;
193	$pid	207	$coro
194	}	208	}
		209
		210	=item async_pool { ... } [@args...]
		211
		212	Similar to C<async>, but uses a coroutine pool, so you should not call
		213	terminate or join on it (although you are allowed to), and you get a
		214	coroutine that might have executed other code already (which can be good
		215	or bad :).
		216
		217	On the plus side, this function is faster than creating (and destroying)
		218	a completly new coroutine, so if you need a lot of generic coroutines in
		219	quick successsion, use C<async_pool>, not C<async>.
		220
		221	The code block is executed in an C<eval> context and a warning will be
		222	issued in case of an exception instead of terminating the program, as
		223	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		224	will not work in the expected way, unless you call terminate or cancel,
		225	which somehow defeats the purpose of pooling (but is fine in the
		226	exceptional case).
		227
		228	The priority will be reset to C<0> after each run, tracing will be
		229	disabled, the description will be reset and the default output filehandle
		230	gets restored, so you can change all these. Otherwise the coroutine will
		231	be re-used "as-is": most notably if you change other per-coroutine global
		232	stuff such as C<$/> 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	$coro
		279	}
		280
		281	=back
		282
		283	=head2 STATIC METHODS
		284
		285	Static methods are actually functions that operate on the current coroutine.
		286
		287	=over 4
195		288
196	=item schedule	289	=item schedule
197		290
198	Calls the scheduler. Please note that the current coroutine will not be put	291	Calls the scheduler. The scheduler will find the next coroutine that is
		292	to be run from the ready queue and switches to it. The next coroutine
		293	to be run is simply the one with the highest priority that is longest
		294	in its ready queue. If there is no coroutine ready, it will clal the
		295	C<$Coro::idle> hook.
		296
		297	Please note that the current coroutine will I<not> be put into the ready
199	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
200	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 >>,
201	ready.	300	thus waking you up.
202		301
203	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.
204		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->cancel (@_);
		346	}
		347
		348	sub killall {
		349	for (Coro::State::list) {
		350	$_->cancel
		351	if $_ != $current && UNIVERSAL::isa $_, "Coro";
205	{	352	}
206	# remember current coroutine	353	}
		354
		355	=back
		356
		357	=head2 COROUTINE METHODS
		358
		359	These are the methods you can call on coroutine objects (or to create
		360	them).
		361
		362	=over 4
		363
		364	=item new Coro \&sub [, @args...]
		365
		366	Create a new coroutine and return it. When the sub returns, the coroutine
		367	automatically terminates as if C<terminate> with the returned values were
		368	called. To make the coroutine run you must first put it into the ready
		369	queue by calling the ready method.
		370
		371	See C<async> and C<Coro::State::new> for additional info about the
		372	coroutine environment.
		373
		374	=cut
		375
		376	sub _run_coro {
		377	terminate &{+shift};
		378	}
		379
		380	sub new {
		381	my $class = shift;
		382
		383	$class->SUPER::new (\&_run_coro, @_)
		384	}
		385
		386	=item $success = $coroutine->ready
		387
		388	Put the given coroutine into the end of its ready queue (there is one
		389	queue for each priority) and return true. If the coroutine is already in
		390	the ready queue, do nothing and return false.
		391
		392	This ensures that the scheduler will resume this coroutine automatically
		393	once all the coroutines of higher priority and all coroutines of the same
		394	priority that were put into the ready queue earlier have been resumed.
		395
		396	=item $is_ready = $coroutine->is_ready
		397
		398	Return whether the coroutine is currently the ready queue or not,
		399
		400	=item $coroutine->cancel (arg...)
		401
		402	Terminates the given coroutine and makes it return the given arguments as
		403	status (default: the empty list). Never returns if the coroutine is the
		404	current coroutine.
		405
		406	=cut
		407
		408	sub cancel {
		409	my $self = shift;
		410	$self->{_status} = [@_];
		411
		412	if ($current == $self) {
		413	push @destroy, $self;
		414	$manager->ready;
		415	&schedule while 1;
		416	} else {
		417	$self->_cancel;
		418	}
		419	}
		420
		421	=item $coroutine->throw ([$scalar])
		422
		423	If C<$throw> is specified and defined, it will be thrown as an exception
		424	inside the coroutine at the next convenient point in time. Otherwise
		425	clears the exception object.
		426
		427	Coro will check for the exception each time a schedule-like-function
		428	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		429	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		430	detect this case and return early in case an exception is pending.
		431
		432	The exception object will be thrown "as is" with the specified scalar in
		433	C<$@>, i.e. if it is a string, no line number or newline will be appended
		434	(unlike with C<die>).
		435
		436	This can be used as a softer means than C<cancel> to ask a coroutine to
		437	end itself, although there is no guarantee that the exception will lead to
		438	termination, and if the exception isn't caught it might well end the whole
		439	program.
		440
		441	You might also think of C<throw> as being the moral equivalent of
		442	C<kill>ing a coroutine with a signal (in this case, a scalar).
		443
		444	=item $coroutine->join
		445
		446	Wait until the coroutine terminates and return any values given to the
		447	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		448	from multiple coroutines, and all will be resumed and given the status
		449	return once the C<$coroutine> terminates.
		450
		451	=cut
		452
		453	sub join {
		454	my $self = shift;
		455
		456	unless ($self->{_status}) {
207	my $current = $Coro::current;	457	my $current = $current;
208		458
209	# register a hypothetical event handler	459	push @{$self->{_on_destroy}}, sub {
210	on_event_invoke sub {
211	# wake up sleeping coroutine
212	$current->ready;	460	$current->ready;
213	undef $current;	461	undef $current;
214	};	462	};
215		463
216	# call schedule until event occured.
217	# in case we are woken up for other reasons
218	# (current still defined), loop.
219	Coro::schedule while $current;	464	&schedule while $current;
220	}	465	}
221		466
222	=item cede
223
224	"Cede" to other coroutines. This function puts the current coroutine into the
225	ready queue and calls C<schedule>, which has the effect of giving up the
226	current "timeslice" to other coroutines of the same or higher priority.
227
228	=item terminate [arg...]
229
230	Terminates the current coroutine with the given status values (see L<cancel>).
231
232	=cut
233
234	sub terminate {
235	$current->cancel (@_);
236	}
237
238	=back
239
240	# dynamic methods
241
242	=head2 COROUTINE METHODS
243
244	These are the methods you can call on coroutine objects.
245
246	=over 4
247
248	=item new Coro \&sub [, @args...]
249
250	Create a new coroutine and return it. When the sub returns the coroutine
251	automatically terminates as if C<terminate> with the returned values were
252	called. To make the coroutine run you must first put it into the ready queue
253	by calling the ready method.
254
255	Calling C<exit> in a coroutine will not work correctly, so do not do that.
256
257	=cut
258
259	sub _new_coro {
260	terminate &{+shift};
261	}
262
263	sub new {
264	my $class = shift;
265
266	$class->SUPER::new (\&_new_coro, @_)
267	}
268
269	=item $success = $coroutine->ready
270
271	Put the given coroutine into the ready queue (according to it's priority)
272	and return true. If the coroutine is already in the ready queue, do nothing
273	and return false.
274
275	=item $is_ready = $coroutine->is_ready
276
277	Return wether the coroutine is currently the ready queue or not,
278
279	=item $coroutine->cancel (arg...)
280
281	Terminates the given coroutine and makes it return the given arguments as
282	status (default: the empty list).
283
284	=cut
285
286	sub cancel {
287	my $self = shift;
288	$self->{status} = [@_];
289	push @destroy, $self;
290	$manager->ready;
291	&schedule if $current == $self;
292	}
293
294	=item $coroutine->join
295
296	Wait until the coroutine terminates and return any values given to the
297	C<terminate> or C<cancel> functions. C<join> can be called multiple times
298	from multiple coroutine.
299
300	=cut
301
302	sub join {
303	my $self = shift;
304	unless ($self->{status}) {
305	push @{$self->{join}}, $current;
306	&schedule;
307	}
308	wantarray ? @{$self->{status}} : $self->{status}[0];	467	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		468	}
		469
		470	=item $coroutine->on_destroy (\&cb)
		471
		472	Registers a callback that is called when this coroutine gets destroyed,
		473	but before it is joined. The callback gets passed the terminate arguments,
		474	if any, and I<must not> die, under any circumstances.
		475
		476	=cut
		477
		478	sub on_destroy {
		479	my ($self, $cb) = @_;
		480
		481	push @{ $self->{_on_destroy} }, $cb;
309	}	482	}
310		483
311	=item $oldprio = $coroutine->prio ($newprio)	484	=item $oldprio = $coroutine->prio ($newprio)
312		485
313	Sets (or gets, if the argument is missing) the priority of the	486	Sets (or gets, if the argument is missing) the priority of the
…		…
336	higher values mean lower priority, just as in unix).	509	higher values mean lower priority, just as in unix).
337		510
338	=item $olddesc = $coroutine->desc ($newdesc)	511	=item $olddesc = $coroutine->desc ($newdesc)
339		512
340	Sets (or gets in case the argument is missing) the description for this	513	Sets (or gets in case the argument is missing) the description for this
341	coroutine. This is just a free-form string you can associate with a coroutine.	514	coroutine. This is just a free-form string you can associate with a
		515	coroutine.
		516
		517	This method simply sets the C<< $coroutine->{desc} >> member to the given
		518	string. You can modify this member directly if you wish.
342		519
343	=cut	520	=cut
344		521
345	sub desc {	522	sub desc {
346	my $old = $_[0]{desc};	523	my $old = $_[0]{desc};
…		…
348	$old;	525	$old;
349	}	526	}
350		527
351	=back	528	=back
352		529
353	=head2 UTILITY FUNCTIONS	530	=head2 GLOBAL FUNCTIONS
354		531
355	=over 4	532	=over 4
356		533
		534	=item Coro::nready
		535
		536	Returns the number of coroutines that are currently in the ready state,
		537	i.e. that can be switched to by calling C<schedule> directory or
		538	indirectly. The value C<0> means that the only runnable coroutine is the
		539	currently running one, so C<cede> would have no effect, and C<schedule>
		540	would cause a deadlock unless there is an idle handler that wakes up some
		541	coroutines.
		542
		543	=item my $guard = Coro::guard { ... }
		544
		545	This creates and returns a guard object. Nothing happens until the object
		546	gets destroyed, in which case the codeblock given as argument will be
		547	executed. This is useful to free locks or other resources in case of a
		548	runtime error or when the coroutine gets canceled, as in both cases the
		549	guard block will be executed. The guard object supports only one method,
		550	C<< ->cancel >>, which will keep the codeblock from being executed.
		551
		552	Example: set some flag and clear it again when the coroutine gets canceled
		553	or the function returns:
		554
		555	sub do_something {
		556	my $guard = Coro::guard { $busy = 0 };
		557	$busy = 1;
		558
		559	# do something that requires $busy to be true
		560	}
		561
		562	=cut
		563
		564	sub guard(&) {
		565	bless \(my $cb = $_[0]), "Coro::guard"
		566	}
		567
		568	sub Coro::guard::cancel {
		569	${$_[0]} = sub { };
		570	}
		571
		572	sub Coro::guard::DESTROY {
		573	${$_[0]}->();
		574	}
		575
		576
357	=item unblock_sub { ... }	577	=item unblock_sub { ... }
358		578
359	This utility function takes a BLOCK or code reference and "unblocks" it,	579	This utility function takes a BLOCK or code reference and "unblocks" it,
360	returning the new coderef. This means that the new coderef will return	580	returning a new coderef. Unblocking means that calling the new coderef
361	immediately without blocking, returning nothing, while the original code	581	will return immediately without blocking, returning nothing, while the
362	ref will be called (with parameters) from within its own coroutine.	582	original code ref will be called (with parameters) from within another
		583	coroutine.
363		584
364	The reason this fucntion exists is that many event libraries (such as the	585	The reason this function exists is that many event libraries (such as the
365	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	586	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
366	of thread-safety). This means you must not block within event callbacks,	587	of thread-safety). This means you must not block within event callbacks,
367	otherwise you might suffer from crashes or worse.	588	otherwise you might suffer from crashes or worse. The only event library
		589	currently known that is safe to use without C<unblock_sub> is L<EV>.
368		590
369	This function allows your callbacks to block by executing them in another	591	This function allows your callbacks to block by executing them in another
370	coroutine where it is safe to block. One example where blocking is handy	592	coroutine where it is safe to block. One example where blocking is handy
371	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	593	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
372	disk.	594	disk, for example.
373		595
374	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	596	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
375	creating event callbacks that want to block.	597	creating event callbacks that want to block.
376		598
377	=cut	599	If your handler does not plan to block (e.g. simply sends a message to
		600	another coroutine, or puts some other coroutine into the ready queue),
		601	there is no reason to use C<unblock_sub>.
378		602
379	our @unblock_pool;	603	Note that you also need to use C<unblock_sub> for any other callbacks that
		604	are indirectly executed by any C-based event loop. For example, when you
		605	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		606	provides callbacks that are the result of some event callback, then you
		607	must not block either, or use C<unblock_sub>.
		608
		609	=cut
		610
380	our @unblock_queue;	611	our @unblock_queue;
381	our $UNBLOCK_POOL_SIZE = 2;
382		612
383	sub unblock_handler_ {	613	# we create a special coro because we want to cede,
384	while () {	614	# to reduce pressure on the coro pool (because most callbacks
385	my ($cb, @arg) = @{ delete $Coro::current->{arg} };	615	# return immediately and can be reused) and because we cannot cede
386	$cb->(@arg);	616	# inside an event callback.
387
388	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
389	push @unblock_pool, $Coro::current;
390	schedule;
391	}
392	}
393
394	our $unblock_scheduler = async {	617	our $unblock_scheduler = new Coro sub {
395	while () {	618	while () {
396	while (my $cb = pop @unblock_queue) {	619	while (my $cb = pop @unblock_queue) {
397	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);	620	# this is an inlined copy of async_pool
398	$handler->{arg} = $cb;	621	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		622
		623	$coro->{_invoke} = $cb;
399	$handler->ready;	624	$coro->ready;
400	cede;	625	cede; # for short-lived callbacks, this reduces pressure on the coro pool
401	}	626	}
402		627	schedule; # sleep well
403	schedule;
404	}	628	}
405	};	629	};
		630	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
406		631
407	sub unblock_sub(&) {	632	sub unblock_sub(&) {
408	my $cb = shift;	633	my $cb = shift;
409		634
410	sub {	635	sub {
411	push @unblock_queue, [$cb, @_];	636	unshift @unblock_queue, [$cb, @_];
412	$unblock_scheduler->ready;	637	$unblock_scheduler->ready;
413	}	638	}
414	}	639	}
415		640
		641	=item $cb = Coro::rouse_cb
		642
		643	Create and return a "rouse callback". That's a code reference that, when
		644	called, will save its arguments and notify the owner coroutine of the
		645	callback.
		646
		647	See the next function.
		648
		649	=item @args = Coro::rouse_wait [$cb]
		650
		651	Wait for the specified rouse callback (or the last one tht was created in
		652	this coroutine).
		653
		654	As soon as the callback is invoked (or when the calback was invoked before
		655	C<rouse_wait>), it will return a copy of the arguments originally passed
		656	to the rouse callback.
		657
		658	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		659
416	=back	660	=back
417		661
418	=cut	662	=cut
419		663
420	1;	664	1;
421		665
		666	=head1 HOW TO WAIT FOR A CALLBACK
		667
		668	It is very common for a coroutine to wait for some callback to be
		669	called. This occurs naturally when you use coroutines in an otherwise
		670	event-based program, or when you use event-based libraries.
		671
		672	These typically register a callback for some event, and call that callback
		673	when the event occured. In a coroutine, however, you typically want to
		674	just wait for the event, simplyifying things.
		675
		676	For example C<< AnyEvent->child >> registers a callback to be called when
		677	a specific child has exited:
		678
		679	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		680
		681	But from withina coroutine, you often just want to write this:
		682
		683	my $status = wait_for_child $pid;
		684
		685	Coro offers two functions specifically designed to make this easy,
		686	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		687
		688	The first function, C<rouse_cb>, generates and returns a callback that,
		689	when invoked, will save it's arguments and notify the coroutine that
		690	created the callback.
		691
		692	The second function, C<rouse_wait>, waits for the callback to be called
		693	(by calling C<schedule> to go to sleep) and returns the arguments
		694	originally passed to the callback.
		695
		696	Using these functions, it becomes easy to write the C<wait_for_child>
		697	function mentioned above:
		698
		699	sub wait_for_child($) {
		700	my ($pid) = @_;
		701
		702	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		703
		704	my ($rpid, $rstatus) = Coro::rouse_wait;
		705	$rstatus
		706	}
		707
		708	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		709	you can roll your own, using C<schedule>:
		710
		711	sub wait_for_child($) {
		712	my ($pid) = @_;
		713
		714	# store the current coroutine in $current,
		715	# and provide result variables for the closure passed to ->child
		716	my $current = $Coro::current;
		717	my ($done, $rstatus);
		718
		719	# pass a closure to ->child
		720	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		721	$rstatus = $_[1]; # remember rstatus
		722	$done = 1; # mark $rstatus as valud
		723	});
		724
		725	# wait until the closure has been called
		726	schedule while !$done;
		727
		728	$rstatus
		729	}
		730
		731
422	=head1 BUGS/LIMITATIONS	732	=head1 BUGS/LIMITATIONS
423		733
424	- you must make very sure that no coro is still active on global	734	=over 4
425	destruction. very bad things might happen otherwise (usually segfaults).
426		735
		736	=item fork with pthread backend
		737
		738	When Coro is compiled using the pthread backend (which isn't recommended
		739	but required on many BSDs as their libcs are completely broken), then
		740	coroutines will not survive a fork. There is no known workaround except to
		741	fix your libc and use a saner backend.
		742
		743	=item perl process emulation ("threads")
		744
427	- this module is not thread-safe. You should only ever use this module	745	This module is not perl-pseudo-thread-safe. You should only ever use this
428	from the same thread (this requirement might be losened in the future	746	module from the same thread (this requirement might be removed in the
429	to allow per-thread schedulers, but Coro::State does not yet allow	747	future to allow per-thread schedulers, but Coro::State does not yet allow
430	this).	748	this). I recommend disabling thread support and using processes, as having
		749	the windows process emulation enabled under unix roughly halves perl
		750	performance, even when not used.
		751
		752	=item coroutine switching not signal safe
		753
		754	You must not switch to another coroutine from within a signal handler
		755	(only relevant with %SIG - most event libraries provide safe signals).
		756
		757	That means you I<MUST NOT> call any function that might "block" the
		758	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		759	anything that calls those. Everything else, including calling C<ready>,
		760	works.
		761
		762	=back
		763
431		764
432	=head1 SEE ALSO	765	=head1 SEE ALSO
433		766
		767	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		768
		769	Debugging: L<Coro::Debug>.
		770
434	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	771	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
435		772
436	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	773	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
437		774
438	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	775	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
439		776
440	Embedding: L<Coro:MakeMaker>	777	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		778
		779	XS API: L<Coro::MakeMaker>.
		780
		781	Low level Configuration, Coroutine Environment: L<Coro::State>.
441		782
442	=head1 AUTHOR	783	=head1 AUTHOR
443		784
444	Marc Lehmann <schmorp@schmorp.de>	785	Marc Lehmann <schmorp@schmorp.de>
445	http://home.schmorp.de/	786	http://home.schmorp.de/

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Revision 1.224 by root, Wed Nov 19 05:52:42 2008 UTC