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

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.95 by root, Sun Dec 3 22:50:06 2006 UTC vs.
Revision 1.222 by root, Tue Nov 18 08:59:46 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 = '3.01';	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.
		301
		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.
202		309
203	The canonical way to wait on external events is this:	310	The canonical way to wait on external events is this:
204		311
205	{	312	{
206	# remember current coroutine	313	# remember current coroutine
…		…
211	# wake up sleeping coroutine	318	# wake up sleeping coroutine
212	$current->ready;	319	$current->ready;
213	undef $current;	320	undef $current;
214	};	321	};
215		322
216	# call schedule until event occured.	323	# call schedule until event occurred.
217	# in case we are woken up for other reasons	324	# in case we are woken up for other reasons
218	# (current still defined), loop.	325	# (current still defined), loop.
219	Coro::schedule while $current;	326	Coro::schedule while $current;
220	}	327	}
221		328
222	=item cede	329	=item cede
223		330
224	"Cede" to other coroutines. This function puts the current coroutine into the	331	"Cede" to other coroutines. This function puts the current coroutine into
225	ready queue and calls C<schedule>, which has the effect of giving up the	332	the ready queue and calls C<schedule>, which has the effect of giving
226	current "timeslice" to other coroutines of the same or higher priority.	333	up the current "timeslice" to other coroutines of the same or higher
		334	priority. Once your coroutine gets its turn again it will automatically be
		335	resumed.
		336
		337	This function is often called C<yield> in other languages.
		338
		339	=item Coro::cede_notself
		340
		341	Works like cede, but is not exported by default and will cede to I<any>
		342	coroutine, regardless of priority. This is useful sometimes to ensure
		343	progress is made.
227		344
228	=item terminate [arg...]	345	=item terminate [arg...]
229		346
230	Terminates the current coroutine with the given status values (see L<cancel>).	347	Terminates the current coroutine with the given status values (see L<cancel>).
		348
		349	=item killall
		350
		351	Kills/terminates/cancels all coroutines except the currently running
		352	one. This is useful after a fork, either in the child or the parent, as
		353	usually only one of them should inherit the running coroutines.
		354
		355	Note that while this will try to free some of the main programs resources,
		356	you cannot free all of them, so if a coroutine that is not the main
		357	program calls this function, there will be some one-time resource leak.
231		358
232	=cut	359	=cut
233		360
234	sub terminate {	361	sub terminate {
235	$current->cancel (@_);	362	$current->cancel (@_);
236	}	363	}
237		364
		365	sub killall {
		366	for (Coro::State::list) {
		367	$_->cancel
		368	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		369	}
		370	}
		371
238	=back	372	=back
239		373
240	# dynamic methods
241
242	=head2 COROUTINE METHODS	374	=head2 COROUTINE METHODS
243		375
244	These are the methods you can call on coroutine objects.	376	These are the methods you can call on coroutine objects (or to create
		377	them).
245		378
246	=over 4	379	=over 4
247		380
248	=item new Coro \&sub [, @args...]	381	=item new Coro \&sub [, @args...]
249		382
250	Create a new coroutine and return it. When the sub returns the coroutine	383	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	384	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	385	called. To make the coroutine run you must first put it into the ready
253	by calling the ready method.	386	queue by calling the ready method.
254		387
255	Calling C<exit> in a coroutine will not work correctly, so do not do that.	388	See C<async> and C<Coro::State::new> for additional info about the
		389	coroutine environment.
256		390
257	=cut	391	=cut
258		392
259	sub _run_coro {	393	sub _run_coro {
260	terminate &{+shift};	394	terminate &{+shift};
…		…
266	$class->SUPER::new (\&_run_coro, @_)	400	$class->SUPER::new (\&_run_coro, @_)
267	}	401	}
268		402
269	=item $success = $coroutine->ready	403	=item $success = $coroutine->ready
270		404
271	Put the given coroutine into the ready queue (according to it's priority)	405	Put the given coroutine into the end of its ready queue (there is one
272	and return true. If the coroutine is already in the ready queue, do nothing	406	queue for each priority) and return true. If the coroutine is already in
273	and return false.	407	the ready queue, do nothing and return false.
		408
		409	This ensures that the scheduler will resume this coroutine automatically
		410	once all the coroutines of higher priority and all coroutines of the same
		411	priority that were put into the ready queue earlier have been resumed.
274		412
275	=item $is_ready = $coroutine->is_ready	413	=item $is_ready = $coroutine->is_ready
276		414
277	Return wether the coroutine is currently the ready queue or not,	415	Return whether the coroutine is currently the ready queue or not,
278		416
279	=item $coroutine->cancel (arg...)	417	=item $coroutine->cancel (arg...)
280		418
281	Terminates the given coroutine and makes it return the given arguments as	419	Terminates the given coroutine and makes it return the given arguments as
282	status (default: the empty list).	420	status (default: the empty list). Never returns if the coroutine is the
		421	current coroutine.
283		422
284	=cut	423	=cut
285		424
286	sub cancel {	425	sub cancel {
287	my $self = shift;	426	my $self = shift;
288	$self->{status} = [@_];	427	$self->{_status} = [@_];
		428
		429	if ($current == $self) {
289	push @destroy, $self;	430	push @destroy, $self;
290	$manager->ready;	431	$manager->ready;
291	&schedule if $current == $self;	432	&schedule while 1;
		433	} else {
		434	$self->_cancel;
		435	}
292	}	436	}
		437
		438	=item $coroutine->throw ([$scalar])
		439
		440	If C<$throw> is specified and defined, it will be thrown as an exception
		441	inside the coroutine at the next convenient point in time. Otherwise
		442	clears the exception object.
		443
		444	Coro will check for the exception each time a schedule-like-function
		445	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		446	>>, C<< Coro::Handle->readable >> and so on. Note that this means that
		447	when a coroutine is acquiring a lock, it might only throw after it has
		448	sucessfully acquired it.
		449
		450	The exception object will be thrown "as is" with the specified scalar in
		451	C<$@>, i.e. if it is a string, no line number or newline will be appended
		452	(unlike with C<die>).
		453
		454	This can be used as a softer means than C<cancel> to ask a coroutine to
		455	end itself, although there is no guarantee that the exception will lead to
		456	termination, and if the exception isn't caught it might well end the whole
		457	program.
		458
		459	You might also think of C<throw> as being the moral equivalent of
		460	C<kill>ing a coroutine with a signal (in this case, a scalar).
293		461
294	=item $coroutine->join	462	=item $coroutine->join
295		463
296	Wait until the coroutine terminates and return any values given to the	464	Wait until the coroutine terminates and return any values given to the
297	C<terminate> or C<cancel> functions. C<join> can be called multiple times	465	C<terminate> or C<cancel> functions. C<join> can be called concurrently
298	from multiple coroutine.	466	from multiple coroutines, and all will be resumed and given the status
		467	return once the C<$coroutine> terminates.
299		468
300	=cut	469	=cut
301		470
302	sub join {	471	sub join {
303	my $self = shift;	472	my $self = shift;
		473
304	unless ($self->{status}) {	474	unless ($self->{_status}) {
305	push @{$self->{join}}, $current;	475	my $current = $current;
306	&schedule;	476
		477	push @{$self->{_on_destroy}}, sub {
		478	$current->ready;
		479	undef $current;
		480	};
		481
		482	&schedule while $current;
307	}	483	}
		484
308	wantarray ? @{$self->{status}} : $self->{status}[0];	485	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		486	}
		487
		488	=item $coroutine->on_destroy (\&cb)
		489
		490	Registers a callback that is called when this coroutine gets destroyed,
		491	but before it is joined. The callback gets passed the terminate arguments,
		492	if any, and I<must not> die, under any circumstances.
		493
		494	=cut
		495
		496	sub on_destroy {
		497	my ($self, $cb) = @_;
		498
		499	push @{ $self->{_on_destroy} }, $cb;
309	}	500	}
310		501
311	=item $oldprio = $coroutine->prio ($newprio)	502	=item $oldprio = $coroutine->prio ($newprio)
312		503
313	Sets (or gets, if the argument is missing) the priority of the	504	Sets (or gets, if the argument is missing) the priority of the
…		…
336	higher values mean lower priority, just as in unix).	527	higher values mean lower priority, just as in unix).
337		528
338	=item $olddesc = $coroutine->desc ($newdesc)	529	=item $olddesc = $coroutine->desc ($newdesc)
339		530
340	Sets (or gets in case the argument is missing) the description for this	531	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.	532	coroutine. This is just a free-form string you can associate with a
		533	coroutine.
		534
		535	This method simply sets the C<< $coroutine->{desc} >> member to the given
		536	string. You can modify this member directly if you wish.
342		537
343	=cut	538	=cut
344		539
345	sub desc {	540	sub desc {
346	my $old = $_[0]{desc};	541	my $old = $_[0]{desc};
…		…
348	$old;	543	$old;
349	}	544	}
350		545
351	=back	546	=back
352		547
353	=head2 UTILITY FUNCTIONS	548	=head2 GLOBAL FUNCTIONS
354		549
355	=over 4	550	=over 4
356		551
		552	=item Coro::nready
		553
		554	Returns the number of coroutines that are currently in the ready state,
		555	i.e. that can be switched to by calling C<schedule> directory or
		556	indirectly. The value C<0> means that the only runnable coroutine is the
		557	currently running one, so C<cede> would have no effect, and C<schedule>
		558	would cause a deadlock unless there is an idle handler that wakes up some
		559	coroutines.
		560
		561	=item my $guard = Coro::guard { ... }
		562
		563	This creates and returns a guard object. Nothing happens until the object
		564	gets destroyed, in which case the codeblock given as argument will be
		565	executed. This is useful to free locks or other resources in case of a
		566	runtime error or when the coroutine gets canceled, as in both cases the
		567	guard block will be executed. The guard object supports only one method,
		568	C<< ->cancel >>, which will keep the codeblock from being executed.
		569
		570	Example: set some flag and clear it again when the coroutine gets canceled
		571	or the function returns:
		572
		573	sub do_something {
		574	my $guard = Coro::guard { $busy = 0 };
		575	$busy = 1;
		576
		577	# do something that requires $busy to be true
		578	}
		579
		580	=cut
		581
		582	sub guard(&) {
		583	bless \(my $cb = $_[0]), "Coro::guard"
		584	}
		585
		586	sub Coro::guard::cancel {
		587	${$_[0]} = sub { };
		588	}
		589
		590	sub Coro::guard::DESTROY {
		591	${$_[0]}->();
		592	}
		593
		594
357	=item unblock_sub { ... }	595	=item unblock_sub { ... }
358		596
359	This utility function takes a BLOCK or code reference and "unblocks" it,	597	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	598	returning a new coderef. Unblocking means that calling the new coderef
361	immediately without blocking, returning nothing, while the original code	599	will return immediately without blocking, returning nothing, while the
362	ref will be called (with parameters) from within its own coroutine.	600	original code ref will be called (with parameters) from within another
		601	coroutine.
363		602
364	The reason this fucntion exists is that many event libraries (such as the	603	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	604	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,	605	of thread-safety). This means you must not block within event callbacks,
367	otherwise you might suffer from crashes or worse.	606	otherwise you might suffer from crashes or worse. The only event library
		607	currently known that is safe to use without C<unblock_sub> is L<EV>.
368		608
369	This function allows your callbacks to block by executing them in another	609	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	610	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	611	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
372	disk.	612	disk, for example.
373		613
374	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	614	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
375	creating event callbacks that want to block.	615	creating event callbacks that want to block.
376		616
377	=cut	617	If your handler does not plan to block (e.g. simply sends a message to
		618	another coroutine, or puts some other coroutine into the ready queue),
		619	there is no reason to use C<unblock_sub>.
378		620
379	our @unblock_pool;	621	Note that you also need to use C<unblock_sub> for any other callbacks that
		622	are indirectly executed by any C-based event loop. For example, when you
		623	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		624	provides callbacks that are the result of some event callback, then you
		625	must not block either, or use C<unblock_sub>.
		626
		627	=cut
		628
380	our @unblock_queue;	629	our @unblock_queue;
381	our $UNBLOCK_POOL_SIZE = 2;
382		630
383	sub unblock_handler_ {	631	# we create a special coro because we want to cede,
384	while () {	632	# to reduce pressure on the coro pool (because most callbacks
385	my ($cb, @arg) = @{ delete $Coro::current->{arg} };	633	# return immediately and can be reused) and because we cannot cede
386	$cb->(@arg);	634	# 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 {	635	our $unblock_scheduler = new Coro sub {
395	while () {	636	while () {
396	while (my $cb = pop @unblock_queue) {	637	while (my $cb = pop @unblock_queue) {
397	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);	638	# this is an inlined copy of async_pool
398	$handler->{arg} = $cb;	639	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		640
		641	$coro->{_invoke} = $cb;
399	$handler->ready;	642	$coro->ready;
400	cede;	643	cede; # for short-lived callbacks, this reduces pressure on the coro pool
401	}	644	}
402		645	schedule; # sleep well
403	schedule;
404	}	646	}
405	};	647	};
		648	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
406		649
407	sub unblock_sub(&) {	650	sub unblock_sub(&) {
408	my $cb = shift;	651	my $cb = shift;
409		652
410	sub {	653	sub {
411	push @unblock_queue, [$cb, @_];	654	unshift @unblock_queue, [$cb, @_];
412	$unblock_scheduler->ready;	655	$unblock_scheduler->ready;
413	}	656	}
414	}	657	}
415		658
416	=back	659	=back
…		…
419		662
420	1;	663	1;
421		664
422	=head1 BUGS/LIMITATIONS	665	=head1 BUGS/LIMITATIONS
423		666
424	- you must make very sure that no coro is still active on global	667	=over 4
425	destruction. very bad things might happen otherwise (usually segfaults).
426		668
		669	=item fork with pthread backend
		670
		671	When Coro is compiled using the pthread backend (which isn't recommended
		672	but required on many BSDs as their libcs are completely broken), then
		673	coroutines will not survive a fork. There is no known workaround except to
		674	fix your libc and use a saner backend.
		675
		676	=item perl process emulation ("threads")
		677
427	- this module is not thread-safe. You should only ever use this module	678	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	679	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	680	future to allow per-thread schedulers, but Coro::State does not yet allow
430	this).	681	this). I recommend disabling thread support and using processes, as having
		682	the windows process emulation enabled under unix roughly halves perl
		683	performance, even when not used.
		684
		685	=item coroutine switching not signal safe
		686
		687	You must not switch to another coroutine from within a signal handler
		688	(only relevant with %SIG - most event libraries provide safe signals).
		689
		690	That means you I<MUST NOT> call any function that might "block" the
		691	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		692	anything that calls those. Everything else, including calling C<ready>,
		693	works.
		694
		695	=back
		696
431		697
432	=head1 SEE ALSO	698	=head1 SEE ALSO
433		699
		700	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		701
		702	Debugging: L<Coro::Debug>.
		703
434	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	704	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
435		705
436	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	706	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
437		707
438	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	708	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
439		709
440	Embedding: L<Coro:MakeMaker>	710	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		711
		712	XS API: L<Coro::MakeMaker>.
		713
		714	Low level Configuration, Coroutine Environment: L<Coro::State>.
441		715
442	=head1 AUTHOR	716	=head1 AUTHOR
443		717
444	Marc Lehmann <schmorp@schmorp.de>	718	Marc Lehmann <schmorp@schmorp.de>
445	http://home.schmorp.de/	719	http://home.schmorp.de/

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Revision 1.222 by root, Tue Nov 18 08:59:46 2008 UTC