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

Comparing Coro/Coro.pm (file contents):
Revision 1.37 by root, Mon Sep 24 02:25:44 2001 UTC vs.
Revision 1.206 by root, Thu Oct 30 09:57:00 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 process 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
26	This module is still experimental, see the BUGS section below.	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.
27		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
28	In this module, coroutines are defined as "callchain + lexical variables	52	In this module, coroutines are defined as "callchain + lexical variables +
29	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own	53	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30	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
31	important global variables.	55	variables (see L<Coro::State> for more configuration).
32		56
33	=cut	57	=cut
34		58
35	package Coro;	59	package Coro;
36		60
		61	use strict;
37	no warnings qw(uninitialized);	62	no warnings "uninitialized";
38		63
39	use Coro::State;	64	use Coro::State;
40		65
41	use base Exporter;	66	use base qw(Coro::State Exporter);
42		67
43	$VERSION = 0.5;	68	our $idle; # idle handler
		69	our $main; # main coroutine
		70	our $current; # current coroutine
44		71
		72	our $VERSION = 4.802;
		73
45	@EXPORT = qw(async cede schedule terminate current);	74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46	%EXPORT_TAGS = (	75	our %EXPORT_TAGS = (
47	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48	);	77	);
49	@EXPORT_OK = @{$EXPORT_TAGS{prio}};	78	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
50		79
51	{	80	=over 4
52	my @async;
53	my $init;
54		81
55	# this way of handling attributes simply is NOT scalable ;()
56	sub import {
57	Coro->export_to_level(1, @_);
58	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
59	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
60	my ($package, $ref) = (shift, shift);
61	my @attrs;
62	for (@_) {
63	if ($_ eq "Coro") {
64	push @async, $ref;
65	unless ($init++) {
66	eval q{
67	sub INIT {
68	&async(pop @async) while @async;
69	}
70	};
71	}
72	} else {
73	push @attrs, $_;
74	}
75	}
76	return $old ? $old->($package, $ref, @attrs) : @attrs;
77	};
78	}
79
80	}
81
82	=item $main	82	=item $Coro::main
83		83
84	This coroutine represents the main program.	84	This variable stores the coroutine object that represents the main
		85	program. While you cna C<ready> it and do most other things you can do to
		86	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		87	whether you are running in the main program or not.
85		88
86	=cut	89	=cut
87		90
88	our $main = new Coro;	91	$main = new Coro;
89		92
90	=item $current (or as function: current)	93	=item $Coro::current
91		94
92	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	95	The coroutine object representing the current coroutine (the last
		96	coroutine that the Coro scheduler switched to). The initial value is
		97	C<$main> (of course).
93		98
		99	This variable is B<strictly> I<read-only>. You can take copies of the
		100	value stored in it and use it as any other coroutine object, but you must
		101	not otherwise modify the variable itself.
		102
94	=cut	103	=cut
		104
		105	$main->{desc} = "[main::]";
95		106
96	# maybe some other module used Coro::Specific before...	107	# maybe some other module used Coro::Specific before...
97	if ($current) {
98	$main->{specific} = $current->{specific};	108	$main->{_specific} = $current->{_specific}
99	}	109	if $current;
100		110
101	our $current = $main;	111	_set_current $main;
102		112
103	sub current() { $current }	113	sub current() { $current } # [DEPRECATED]
104		114
105	=item $idle	115	=item $Coro::idle
106		116
107	The coroutine to switch to when no other coroutine is running. The default	117	This variable is mainly useful to integrate Coro into event loops. It is
108	implementation prints "FATAL: deadlock detected" and exits.	118	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
		119	pretty low-level functionality.
109		120
110	=cut	121	This variable stores a callback that is called whenever the scheduler
		122	finds no ready coroutines to run. The default implementation prints
		123	"FATAL: deadlock detected" and exits, because the program has no other way
		124	to continue.
111		125
112	# should be done using priorities :(	126	This hook is overwritten by modules such as C<Coro::Timer> and
113	our $idle = new Coro sub {	127	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
114	print STDERR "FATAL: deadlock detected\n";	128	coroutine so the scheduler can run it.
115	exit(51);	129
		130	Note that the callback I<must not>, under any circumstances, block
		131	the current coroutine. Normally, this is achieved by having an "idle
		132	coroutine" that calls the event loop and then blocks again, and then
		133	readying that coroutine in the idle handler.
		134
		135	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		136	technique.
		137
		138	Please note that if your callback recursively invokes perl (e.g. for event
		139	handlers), then it must be prepared to be called recursively itself.
		140
		141	=cut
		142
		143	$idle = sub {
		144	require Carp;
		145	Carp::croak ("FATAL: deadlock detected");
116	};	146	};
		147
		148	sub _cancel {
		149	my ($self) = @_;
		150
		151	# free coroutine data and mark as destructed
		152	$self->_destroy
		153	or return;
		154
		155	# call all destruction callbacks
		156	$_->(@{$self->{_status}})
		157	for @{(delete $self->{_on_destroy}) \|\| []};
		158	}
117		159
118	# this coroutine is necessary because a coroutine	160	# this coroutine is necessary because a coroutine
119	# cannot destroy itself.	161	# cannot destroy itself.
120	my @destroy;	162	my @destroy;
		163	my $manager;
		164
121	my $manager = new Coro sub {	165	$manager = new Coro sub {
122	while() {	166	while () {
123	# by overwriting the state object with the manager we destroy it	167	(shift @destroy)->_cancel
124	# while still being able to schedule this coroutine (in case it has	168	while @destroy;
125	# been readied multiple times. this is harmless since the manager	169
126	# can be called as many times as neccessary and will always
127	# remove itself from the runqueue
128	(pop @destroy)->{_coro_state} = $manager->{_coro_state} while @destroy;
129	&schedule;	170	&schedule;
130	}	171	}
131	};	172	};
		173	$manager->desc ("[coro manager]");
		174	$manager->prio (PRIO_MAX);
132		175
133	# static methods. not really.	176	=back
134		177
135	=head2 STATIC METHODS	178	=head2 SIMPLE COROUTINE CREATION
136
137	Static methods are actually functions that operate on the current process only.
138		179
139	=over 4	180	=over 4
140		181
141	=item async { ... } [@args...]	182	=item async { ... } [@args...]
142		183
143	Create a new asynchronous process and return it's process object	184	Create a new coroutine and return it's coroutine object (usually
144	(usually unused). When the sub returns the new process is automatically	185	unused). The coroutine will be put into the ready queue, so
		186	it will start running automatically on the next scheduler run.
		187
		188	The first argument is a codeblock/closure that should be executed in the
		189	coroutine. When it returns argument returns the coroutine is automatically
145	terminated.	190	terminated.
146		191
		192	The remaining arguments are passed as arguments to the closure.
		193
		194	See the C<Coro::State::new> constructor for info about the coroutine
		195	environment in which coroutines are executed.
		196
		197	Calling C<exit> in a coroutine will do the same as calling exit outside
		198	the coroutine. Likewise, when the coroutine dies, the program will exit,
		199	just as it would in the main program.
		200
		201	If you do not want that, you can provide a default C<die> handler, or
		202	simply avoid dieing (by use of C<eval>).
		203
147	# create a new coroutine that just prints its arguments	204	Example: Create a new coroutine that just prints its arguments.
		205
148	async {	206	async {
149	print "@_\n";	207	print "@_\n";
150	} 1,2,3,4;	208	} 1,2,3,4;
151		209
152	The coderef you submit MUST NOT be a closure that refers to variables
153	in an outer scope. This does NOT work. Pass arguments into it instead.
154
155	=cut	210	=cut
156		211
157	sub async(&@) {	212	sub async(&@) {
158	my $pid = new Coro @_;	213	my $coro = new Coro @_;
159	$manager->ready; # this ensures that the stack is cloned from the manager
160	$pid->ready;	214	$coro->ready;
161	$pid;	215	$coro
162	}	216	}
		217
		218	=item async_pool { ... } [@args...]
		219
		220	Similar to C<async>, but uses a coroutine pool, so you should not call
		221	terminate or join on it (although you are allowed to), and you get a
		222	coroutine that might have executed other code already (which can be good
		223	or bad :).
		224
		225	On the plus side, this function is faster than creating (and destroying)
		226	a completly new coroutine, so if you need a lot of generic coroutines in
		227	quick successsion, use C<async_pool>, not C<async>.
		228
		229	The code block is executed in an C<eval> context and a warning will be
		230	issued in case of an exception instead of terminating the program, as
		231	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		232	will not work in the expected way, unless you call terminate or cancel,
		233	which somehow defeats the purpose of pooling (but is fine in the
		234	exceptional case).
		235
		236	The priority will be reset to C<0> after each run, tracing will be
		237	disabled, the description will be reset and the default output filehandle
		238	gets restored, so you can change all these. Otherwise the coroutine will
		239	be re-used "as-is": most notably if you change other per-coroutine global
		240	stuff such as C<$/> you I<must needs> revert that change, which is most
		241	simply done by using local as in: C<< local $/ >>.
		242
		243	The idle pool size is limited to C<8> idle coroutines (this can be
		244	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		245	coros as required.
		246
		247	If you are concerned about pooled coroutines growing a lot because a
		248	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		249	{ terminate }> once per second or so to slowly replenish the pool. In
		250	addition to that, when the stacks used by a handler grows larger than 16kb
		251	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		252
		253	=cut
		254
		255	our $POOL_SIZE = 8;
		256	our $POOL_RSS = 16 * 1024;
		257	our @async_pool;
		258
		259	sub pool_handler {
		260	my $cb;
		261
		262	while () {
		263	eval {
		264	while () {
		265	_pool_1 $cb;
		266	&$cb;
		267	_pool_2 $cb;
		268	&schedule;
		269	}
		270	};
		271
		272	if ($@) {
		273	last if $@ eq "\3async_pool terminate\2\n";
		274	warn $@;
		275	}
		276	}
		277	}
		278
		279	sub async_pool(&@) {
		280	# this is also inlined into the unlock_scheduler
		281	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		282
		283	$coro->{_invoke} = [@_];
		284	$coro->ready;
		285
		286	$coro
		287	}
		288
		289	=back
		290
		291	=head2 STATIC METHODS
		292
		293	Static methods are actually functions that operate on the current coroutine.
		294
		295	=over 4
163		296
164	=item schedule	297	=item schedule
165		298
166	Calls the scheduler. Please note that the current process will not be put	299	Calls the scheduler. The scheduler will find the next coroutine that is
		300	to be run from the ready queue and switches to it. The next coroutine
		301	to be run is simply the one with the highest priority that is longest
		302	in its ready queue. If there is no coroutine ready, it will clal the
		303	C<$Coro::idle> hook.
		304
		305	Please note that the current coroutine will I<not> be put into the ready
167	into the ready queue, so calling this function usually means you will	306	queue, so calling this function usually means you will never be called
168	never be called again.	307	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		308	thus waking you up.
169		309
170	=cut	310	This makes C<schedule> I<the> generic method to use to block the current
		311	coroutine and wait for events: first you remember the current coroutine in
		312	a variable, then arrange for some callback of yours to call C<< ->ready
		313	>> on that once some event happens, and last you call C<schedule> to put
		314	yourself to sleep. Note that a lot of things can wake your coroutine up,
		315	so you need to check whether the event indeed happened, e.g. by storing the
		316	status in a variable.
		317
		318	The canonical way to wait on external events is this:
		319
		320	{
		321	# remember current coroutine
		322	my $current = $Coro::current;
		323
		324	# register a hypothetical event handler
		325	on_event_invoke sub {
		326	# wake up sleeping coroutine
		327	$current->ready;
		328	undef $current;
		329	};
		330
		331	# call schedule until event occurred.
		332	# in case we are woken up for other reasons
		333	# (current still defined), loop.
		334	Coro::schedule while $current;
		335	}
171		336
172	=item cede	337	=item cede
173		338
174	"Cede" to other processes. This function puts the current process into the	339	"Cede" to other coroutines. This function puts the current coroutine into
175	ready queue and calls C<schedule>, which has the effect of giving up the	340	the ready queue and calls C<schedule>, which has the effect of giving
176	current "timeslice" to other coroutines of the same or higher priority.	341	up the current "timeslice" to other coroutines of the same or higher
		342	priority. Once your coroutine gets its turn again it will automatically be
		343	resumed.
177		344
178	=cut	345	This function is often called C<yield> in other languages.
179		346
		347	=item Coro::cede_notself
		348
		349	Works like cede, but is not exported by default and will cede to I<any>
		350	coroutine, regardless of priority. This is useful sometimes to ensure
		351	progress is made.
		352
180	=item terminate	353	=item terminate [arg...]
181		354
182	Terminates the current process.	355	Terminates the current coroutine with the given status values (see L<cancel>).
183		356
184	Future versions of this function will allow result arguments.	357	=item killall
		358
		359	Kills/terminates/cancels all coroutines except the currently running
		360	one. This is useful after a fork, either in the child or the parent, as
		361	usually only one of them should inherit the running coroutines.
		362
		363	Note that while this will try to free some of the main programs resources,
		364	you cannot free all of them, so if a coroutine that is not the main
		365	program calls this function, there will be some one-time resource leak.
185		366
186	=cut	367	=cut
187		368
188	sub terminate {	369	sub terminate {
189	$current->cancel;	370	$current->cancel (@_);
190	&schedule;	371	}
191	die; # NORETURN	372
		373	sub killall {
		374	for (Coro::State::list) {
		375	$_->cancel
		376	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		377	}
192	}	378	}
193		379
194	=back	380	=back
195		381
196	# dynamic methods
197
198	=head2 PROCESS METHODS	382	=head2 COROUTINE METHODS
199		383
200	These are the methods you can call on process objects.	384	These are the methods you can call on coroutine objects (or to create
		385	them).
201		386
202	=over 4	387	=over 4
203		388
204	=item new Coro \&sub [, @args...]	389	=item new Coro \&sub [, @args...]
205		390
206	Create a new process and return it. When the sub returns the process	391	Create a new coroutine and return it. When the sub returns, the coroutine
207	automatically terminates. To start the process you must first put it into	392	automatically terminates as if C<terminate> with the returned values were
		393	called. To make the coroutine run you must first put it into the ready
208	the ready queue by calling the ready method.	394	queue by calling the ready method.
209		395
210	The coderef you submit MUST NOT be a closure that refers to variables	396	See C<async> and C<Coro::State::new> for additional info about the
211	in an outer scope. This does NOT work. Pass arguments into it instead.	397	coroutine environment.
212		398
213	=cut	399	=cut
214		400
215	sub _newcoro {	401	sub _run_coro {
216	terminate &{+shift};	402	terminate &{+shift};
217	}	403	}
218		404
219	sub new {	405	sub new {
220	my $class = shift;	406	my $class = shift;
221	bless {
222	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
223	}, $class;
224	}
225		407
226	=item $process->ready	408	$class->SUPER::new (\&_run_coro, @_)
		409	}
227		410
228	Put the current process into the ready queue.	411	=item $success = $coroutine->ready
229		412
230	=cut	413	Put the given coroutine into the end of its ready queue (there is one
		414	queue for each priority) and return true. If the coroutine is already in
		415	the ready queue, do nothing and return false.
231		416
232	=item $process->cancel	417	This ensures that the scheduler will resume this coroutine automatically
		418	once all the coroutines of higher priority and all coroutines of the same
		419	priority that were put into the ready queue earlier have been resumed.
233		420
234	Like C<terminate>, but terminates the specified process instead.	421	=item $is_ready = $coroutine->is_ready
		422
		423	Return whether the coroutine is currently the ready queue or not,
		424
		425	=item $coroutine->cancel (arg...)
		426
		427	Terminates the given coroutine and makes it return the given arguments as
		428	status (default: the empty list). Never returns if the coroutine is the
		429	current coroutine.
235		430
236	=cut	431	=cut
237		432
238	sub cancel {	433	sub cancel {
		434	my $self = shift;
		435	$self->{_status} = [@_];
		436
		437	if ($current == $self) {
239	push @destroy, $_[0];	438	push @destroy, $self;
240	$manager->ready;	439	$manager->ready;
241	&schedule if $current == $_[0];	440	&schedule while 1;
		441	} else {
		442	$self->_cancel;
		443	}
242	}	444	}
243		445
		446	=item $coroutine->join
		447
		448	Wait until the coroutine terminates and return any values given to the
		449	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		450	from multiple coroutines, and all will be resumed and given the status
		451	return once the C<$coroutine> terminates.
		452
		453	=cut
		454
		455	sub join {
		456	my $self = shift;
		457
		458	unless ($self->{_status}) {
		459	my $current = $current;
		460
		461	push @{$self->{_on_destroy}}, sub {
		462	$current->ready;
		463	undef $current;
		464	};
		465
		466	&schedule while $current;
		467	}
		468
		469	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		470	}
		471
		472	=item $coroutine->on_destroy (\&cb)
		473
		474	Registers a callback that is called when this coroutine gets destroyed,
		475	but before it is joined. The callback gets passed the terminate arguments,
		476	if any, and I<must not> die, under any circumstances.
		477
		478	=cut
		479
		480	sub on_destroy {
		481	my ($self, $cb) = @_;
		482
		483	push @{ $self->{_on_destroy} }, $cb;
		484	}
		485
244	=item $oldprio = $process->prio($newprio)	486	=item $oldprio = $coroutine->prio ($newprio)
245		487
246	Sets the priority of the process. Higher priority processes get run before	488	Sets (or gets, if the argument is missing) the priority of the
247	lower priority processes. Priorities are smalled signed integer (currently	489	coroutine. Higher priority coroutines get run before lower priority
		490	coroutines. Priorities are small signed integers (currently -4 .. +3),
248	-4 .. +3), that you can refer to using PRIO_xxx constants (use the import	491	that you can refer to using PRIO_xxx constants (use the import tag :prio
249	tag :prio to get then):	492	to get then):
250		493
251	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	494	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
252	3 > 1 > 0 > -1 > -3 > -4	495	3 > 1 > 0 > -1 > -3 > -4
253		496
254	# set priority to HIGH	497	# set priority to HIGH
255	current->prio(PRIO_HIGH);	498	current->prio(PRIO_HIGH);
256		499
257	The idle coroutine ($Coro::idle) always has a lower priority than any	500	The idle coroutine ($Coro::idle) always has a lower priority than any
258	existing coroutine.	501	existing coroutine.
259		502
260	Changing the priority of the current process will take effect immediately,	503	Changing the priority of the current coroutine will take effect immediately,
261	but changing the priority of processes in the ready queue (but not	504	but changing the priority of coroutines in the ready queue (but not
262	running) will only take effect after the next schedule (of that	505	running) will only take effect after the next schedule (of that
263	process). This is a bug that will be fixed in some future version.	506	coroutine). This is a bug that will be fixed in some future version.
264		507
265	=cut
266
267	sub prio {
268	my $old = $_[0]{prio};
269	$_[0]{prio} = $_[1] if @_ > 1;
270	$old;
271	}
272
273	=item $newprio = $process->nice($change)	508	=item $newprio = $coroutine->nice ($change)
274		509
275	Similar to C<prio>, but subtract the given value from the priority (i.e.	510	Similar to C<prio>, but subtract the given value from the priority (i.e.
276	higher values mean lower priority, just as in unix).	511	higher values mean lower priority, just as in unix).
277		512
278	=cut	513	=item $olddesc = $coroutine->desc ($newdesc)
279		514
280	sub nice {	515	Sets (or gets in case the argument is missing) the description for this
281	$_[0]{prio} -= $_[1];	516	coroutine. This is just a free-form string you can associate with a coroutine.
		517
		518	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
		519	can modify this member directly if you wish.
		520
		521	=item $coroutine->throw ([$scalar])
		522
		523	If C<$throw> is specified and defined, it will be thrown as an exception
		524	inside the coroutine at the next convinient point in time (usually after
		525	it gains control at the next schedule/transfer/cede). Otherwise clears the
		526	exception object.
		527
		528	The exception object will be thrown "as is" with the specified scalar in
		529	C<$@>, i.e. if it is a string, no line number or newline will be appended
		530	(unlike with C<die>).
		531
		532	This can be used as a softer means than C<cancel> to ask a coroutine to
		533	end itself, although there is no guarentee that the exception will lead to
		534	termination, and if the exception isn't caught it might well end the whole
		535	program.
		536
		537	=cut
		538
		539	sub desc {
		540	my $old = $_[0]{desc};
		541	$_[0]{desc} = $_[1] if @_ > 1;
		542	$old;
282	}	543	}
283		544
284	=back	545	=back
285		546
		547	=head2 GLOBAL FUNCTIONS
		548
		549	=over 4
		550
		551	=item Coro::nready
		552
		553	Returns the number of coroutines that are currently in the ready state,
		554	i.e. that can be switched to by calling C<schedule> directory or
		555	indirectly. The value C<0> means that the only runnable coroutine is the
		556	currently running one, so C<cede> would have no effect, and C<schedule>
		557	would cause a deadlock unless there is an idle handler that wakes up some
		558	coroutines.
		559
		560	=item my $guard = Coro::guard { ... }
		561
		562	This creates and returns a guard object. Nothing happens until the object
		563	gets destroyed, in which case the codeblock given as argument will be
		564	executed. This is useful to free locks or other resources in case of a
		565	runtime error or when the coroutine gets canceled, as in both cases the
		566	guard block will be executed. The guard object supports only one method,
		567	C<< ->cancel >>, which will keep the codeblock from being executed.
		568
		569	Example: set some flag and clear it again when the coroutine gets canceled
		570	or the function returns:
		571
		572	sub do_something {
		573	my $guard = Coro::guard { $busy = 0 };
		574	$busy = 1;
		575
		576	# do something that requires $busy to be true
		577	}
		578
		579	=cut
		580
		581	sub guard(&) {
		582	bless \(my $cb = $_[0]), "Coro::guard"
		583	}
		584
		585	sub Coro::guard::cancel {
		586	${$_[0]} = sub { };
		587	}
		588
		589	sub Coro::guard::DESTROY {
		590	${$_[0]}->();
		591	}
		592
		593
		594	=item unblock_sub { ... }
		595
		596	This utility function takes a BLOCK or code reference and "unblocks" it,
		597	returning a new coderef. Unblocking means that calling the new coderef
		598	will return immediately without blocking, returning nothing, while the
		599	original code ref will be called (with parameters) from within another
		600	coroutine.
		601
		602	The reason this function exists is that many event libraries (such as the
		603	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		604	of thread-safety). This means you must not block within event callbacks,
		605	otherwise you might suffer from crashes or worse. The only event library
		606	currently known that is safe to use without C<unblock_sub> is L<EV>.
		607
		608	This function allows your callbacks to block by executing them in another
		609	coroutine where it is safe to block. One example where blocking is handy
		610	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		611	disk, for example.
		612
		613	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		614	creating event callbacks that want to block.
		615
		616	If your handler does not plan to block (e.g. simply sends a message to
		617	another coroutine, or puts some other coroutine into the ready queue),
		618	there is no reason to use C<unblock_sub>.
		619
		620	Note that you also need to use C<unblock_sub> for any other callbacks that
		621	are indirectly executed by any C-based event loop. For example, when you
		622	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		623	provides callbacks that are the result of some event callback, then you
		624	must not block either, or use C<unblock_sub>.
		625
		626	=cut
		627
		628	our @unblock_queue;
		629
		630	# we create a special coro because we want to cede,
		631	# to reduce pressure on the coro pool (because most callbacks
		632	# return immediately and can be reused) and because we cannot cede
		633	# inside an event callback.
		634	our $unblock_scheduler = new Coro sub {
		635	while () {
		636	while (my $cb = pop @unblock_queue) {
		637	# this is an inlined copy of async_pool
		638	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		639
		640	$coro->{_invoke} = $cb;
		641	$coro->ready;
		642	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		643	}
		644	schedule; # sleep well
		645	}
		646	};
		647	$unblock_scheduler->desc ("[unblock_sub scheduler]");
		648
		649	sub unblock_sub(&) {
		650	my $cb = shift;
		651
		652	sub {
		653	unshift @unblock_queue, [$cb, @_];
		654	$unblock_scheduler->ready;
		655	}
		656	}
		657
		658	=back
		659
286	=cut	660	=cut
287		661
288	1;	662	1;
289		663
290	=head1 BUGS/LIMITATIONS	664	=head1 BUGS/LIMITATIONS
291		665
292	- you must make very sure that no coro is still active on global destruction.	666	This module is not perl-pseudo-thread-safe. You should only ever use this
293	very bad things might happen otherwise (usually segfaults).
294	- this module is not thread-safe. You must only ever use this module from
295	the same thread (this requirement might be loosened in the future to	667	module from the same thread (this requirement might be removed in the
296	allow per-thread schedulers, but Coro::State does not yet allow this).	668	future to allow per-thread schedulers, but Coro::State does not yet allow
		669	this). I recommend disabling thread support and using processes, as this
		670	is much faster and uses less memory.
297		671
298	=head1 SEE ALSO	672	=head1 SEE ALSO
299		673
300	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	674	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
301	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,	675
302	L<Coro::Handle>, L<Coro::Socket>.	676	Debugging: L<Coro::Debug>.
		677
		678	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		679
		680	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		681
		682	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		683
		684	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		685
		686	XS API: L<Coro::MakeMaker>.
		687
		688	Low level Configuration, Coroutine Environment: L<Coro::State>.
303		689
304	=head1 AUTHOR	690	=head1 AUTHOR
305		691
306	Marc Lehmann <pcg@goof.com>	692	Marc Lehmann <schmorp@schmorp.de>
307	http://www.goof.com/pcg/marc/	693	http://home.schmorp.de/
308		694
309	=cut	695	=cut
310		696

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Revision 1.206 by root, Thu Oct 30 09:57:00 2008 UTC