[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 1.191 by root, Sat May 31 12:10:55 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	my $lock = new Coro::Semaphore;
19	cede;	22	my $locked;
		23
		24	$lock->down;
		25	$locked = 1;
		26	$lock->up;
20		27
21	=head1 DESCRIPTION	28	=head1 DESCRIPTION
22		29
23	This module collection manages coroutines. Coroutines are similar to	30	This module collection manages coroutines. Coroutines are similar to
24	Threads but don't run in parallel.	31	threads but don't (in general) run in parallel at the same time even
		32	on SMP machines. The specific flavor of coroutine used in this module
		33	also guarantees you that it will not switch between coroutines unless
		34	necessary, at easily-identified points in your program, so locking and
		35	parallel access are rarely an issue, making coroutine programming much
		36	safer and easier than threads programming.
25		37
26	This module is still experimental, see the BUGS section below.	38	Unlike a normal perl program, however, coroutines allow you to have
		39	multiple running interpreters that share data, which is especially useful
		40	to code pseudo-parallel processes and for event-based programming, such as
		41	multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to
		42	learn more.
27		43
		44	Coroutines are also useful because Perl has no support for threads (the so
		45	called "threads" that perl offers are nothing more than the (bad) process
		46	emulation coming from the Windows platform: On standard operating systems
		47	they serve no purpose whatsoever, except by making your programs slow and
		48	making them use a lot of memory. Best disable them when building perl, or
		49	aks your software vendor/distributor to do it for you).
		50
28	In this module, coroutines are defined as "callchain + lexical variables	51	In this module, coroutines are defined as "callchain + lexical variables +
29	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own	52	@_ + $_ + $@ + $/ + 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	53	its own set of lexicals and its own set of perls most important global
31	important global variables.	54	variables (see L<Coro::State> for more configuration).
32		55
33	=cut	56	=cut
34		57
35	package Coro;	58	package Coro;
36		59
		60	use strict;
37	no warnings qw(uninitialized);	61	no warnings "uninitialized";
38		62
39	use Coro::State;	63	use Coro::State;
40		64
41	use base Exporter;	65	use base qw(Coro::State Exporter);
42		66
43	$VERSION = 0.5;	67	our $idle; # idle handler
		68	our $main; # main coroutine
		69	our $current; # current coroutine
44		70
		71	our $VERSION = 4.742;
		72
45	@EXPORT = qw(async cede schedule terminate current);	73	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46	%EXPORT_TAGS = (	74	our %EXPORT_TAGS = (
47	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	75	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48	);	76	);
49	@EXPORT_OK = @{$EXPORT_TAGS{prio}};	77	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
50		78
51	{	79	=over 4
52	my @async;
53	my $init;
54		80
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	81	=item $Coro::main
83		82
84	This coroutine represents the main program.	83	This variable stores the coroutine object that represents the main
		84	program. While you cna C<ready> it and do most other things you can do to
		85	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		86	wether you are running in the main program or not.
85		87
86	=cut	88	=cut
87		89
88	our $main = new Coro;	90	$main = new Coro;
89		91
90	=item $current (or as function: current)	92	=item $Coro::current
91		93
92	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	94	The coroutine object representing the current coroutine (the last
		95	coroutine that the Coro scheduler switched to). The initial value is
		96	C<$main> (of course).
93		97
		98	This variable is B<strictly> I<read-only>. You can take copies of the
		99	value stored in it and use it as any other coroutine object, but you must
		100	not otherwise modify the variable itself.
		101
94	=cut	102	=cut
		103
		104	$main->{desc} = "[main::]";
95		105
96	# maybe some other module used Coro::Specific before...	106	# maybe some other module used Coro::Specific before...
97	if ($current) {
98	$main->{specific} = $current->{specific};	107	$main->{_specific} = $current->{_specific}
99	}	108	if $current;
100		109
101	our $current = $main;	110	_set_current $main;
102		111
103	sub current() { $current }	112	sub current() { $current } # [DEPRECATED]
104		113
105	=item $idle	114	=item $Coro::idle
106		115
107	The coroutine to switch to when no other coroutine is running. The default	116	This variable is mainly useful to integrate Coro into event loops. It is
108	implementation prints "FATAL: deadlock detected" and exits.	117	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
		118	pretty low-level functionality.
109		119
110	=cut	120	This variable stores a callback that is called whenever the scheduler
		121	finds no ready coroutines to run. The default implementation prints
		122	"FATAL: deadlock detected" and exits, because the program has no other way
		123	to continue.
111		124
112	# should be done using priorities :(	125	This hook is overwritten by modules such as C<Coro::Timer> and
113	our $idle = new Coro sub {	126	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
114	print STDERR "FATAL: deadlock detected\n";	127	coroutine so the scheduler can run it.
115	exit(51);	128
		129	Note that the callback I<must not>, under any circumstances, block
		130	the current coroutine. Normally, this is achieved by having an "idle
		131	coroutine" that calls the event loop and then blocks again, and then
		132	readying that coroutine in the idle handler.
		133
		134	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		135	technique.
		136
		137	Please note that if your callback recursively invokes perl (e.g. for event
		138	handlers), then it must be prepared to be called recursively itself.
		139
		140	=cut
		141
		142	$idle = sub {
		143	require Carp;
		144	Carp::croak ("FATAL: deadlock detected");
116	};	145	};
		146
		147	sub _cancel {
		148	my ($self) = @_;
		149
		150	# free coroutine data and mark as destructed
		151	$self->_destroy
		152	or return;
		153
		154	# call all destruction callbacks
		155	$_->(@{$self->{_status}})
		156	for @{(delete $self->{_on_destroy}) \|\| []};
		157	}
117		158
118	# this coroutine is necessary because a coroutine	159	# this coroutine is necessary because a coroutine
119	# cannot destroy itself.	160	# cannot destroy itself.
120	my @destroy;	161	my @destroy;
		162	my $manager;
		163
121	my $manager = new Coro sub {	164	$manager = new Coro sub {
122	while() {	165	while () {
123	# by overwriting the state object with the manager we destroy it	166	(shift @destroy)->_cancel
124	# while still being able to schedule this coroutine (in case it has	167	while @destroy;
125	# been readied multiple times. this is harmless since the manager	168
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;	169	&schedule;
130	}	170	}
131	};	171	};
		172	$manager->desc ("[coro manager]");
		173	$manager->prio (PRIO_MAX);
132		174
133	# static methods. not really.	175	=back
134		176
135	=head2 STATIC METHODS	177	=head2 SIMPLE COROUTINE CREATION
136
137	Static methods are actually functions that operate on the current process only.
138		178
139	=over 4	179	=over 4
140		180
141	=item async { ... } [@args...]	181	=item async { ... } [@args...]
142		182
143	Create a new asynchronous process and return it's process object	183	Create a new coroutine and return it's coroutine object (usually
144	(usually unused). When the sub returns the new process is automatically	184	unused). The coroutine will be put into the ready queue, so
		185	it will start running automatically on the next scheduler run.
		186
		187	The first argument is a codeblock/closure that should be executed in the
		188	coroutine. When it returns argument returns the coroutine is automatically
145	terminated.	189	terminated.
146		190
		191	The remaining arguments are passed as arguments to the closure.
		192
		193	See the C<Coro::State::new> constructor for info about the coroutine
		194	environment in which coroutines are executed.
		195
		196	Calling C<exit> in a coroutine will do the same as calling exit outside
		197	the coroutine. Likewise, when the coroutine dies, the program will exit,
		198	just as it would in the main program.
		199
		200	If you do not want that, you can provide a default C<die> handler, or
		201	simply avoid dieing (by use of C<eval>).
		202
147	# create a new coroutine that just prints its arguments	203	Example: Create a new coroutine that just prints its arguments.
		204
148	async {	205	async {
149	print "@_\n";	206	print "@_\n";
150	} 1,2,3,4;	207	} 1,2,3,4;
151		208
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	209	=cut
156		210
157	sub async(&@) {	211	sub async(&@) {
158	my $pid = new Coro @_;	212	my $coro = new Coro @_;
159	$manager->ready; # this ensures that the stack is cloned from the manager
160	$pid->ready;	213	$coro->ready;
161	$pid;	214	$coro
162	}	215	}
		216
		217	=item async_pool { ... } [@args...]
		218
		219	Similar to C<async>, but uses a coroutine pool, so you should not call
		220	terminate or join on it (although you are allowed to), and you get a
		221	coroutine that might have executed other code already (which can be good
		222	or bad :).
		223
		224	On the plus side, this function is faster than creating (and destroying)
		225	a completely new coroutine, so if you need a lot of generic coroutines in
		226	quick successsion, use C<async_pool>, not C<async>.
		227
		228	The code block is executed in an C<eval> context and a warning will be
		229	issued in case of an exception instead of terminating the program, as
		230	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		231	will not work in the expected way, unless you call terminate or cancel,
		232	which somehow defeats the purpose of pooling (but is fine in the
		233	exceptional case).
		234
		235	The priority will be reset to C<0> after each run, tracing will be
		236	disabled, the description will be reset and the default output filehandle
		237	gets restored, so you can change all these. Otherwise the coroutine will
		238	be re-used "as-is": most notably if you change other per-coroutine global
		239	stuff such as C<$/> you I<must needs> to revert that change, which is most
		240	simply done by using local as in: C< local $/ >.
		241
		242	The pool size is limited to C<8> idle coroutines (this can be adjusted by
		243	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		244	required.
		245
		246	If you are concerned about pooled coroutines growing a lot because a
		247	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		248	{ terminate }> once per second or so to slowly replenish the pool. In
		249	addition to that, when the stacks used by a handler grows larger than 16kb
		250	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		251
		252	=cut
		253
		254	our $POOL_SIZE = 8;
		255	our $POOL_RSS = 16 * 1024;
		256	our @async_pool;
		257
		258	sub pool_handler {
		259	my $cb;
		260
		261	while () {
		262	eval {
		263	while () {
		264	_pool_1 $cb;
		265	&$cb;
		266	_pool_2 $cb;
		267	&schedule;
		268	}
		269	};
		270
		271	last if $@ eq "\3async_pool terminate\2\n";
		272	warn $@ if $@;
		273	}
		274	}
		275
		276	sub async_pool(&@) {
		277	# this is also inlined into the unlock_scheduler
		278	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		279
		280	$coro->{_invoke} = [@_];
		281	$coro->ready;
		282
		283	$coro
		284	}
		285
		286	=back
		287
		288	=head2 STATIC METHODS
		289
		290	Static methods are actually functions that operate on the current coroutine.
		291
		292	=over 4
163		293
164	=item schedule	294	=item schedule
165		295
166	Calls the scheduler. Please note that the current process will not be put	296	Calls the scheduler. The scheduler will find the next coroutine that is
		297	to be run from the ready queue and switches to it. The next coroutine
		298	to be run is simply the one with the highest priority that is longest
		299	in its ready queue. If there is no coroutine ready, it will clal the
		300	C<$Coro::idle> hook.
		301
		302	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	303	queue, so calling this function usually means you will never be called
168	never be called again.	304	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		305	thus waking you up.
169		306
170	=cut	307	This makes C<schedule> I<the> generic method to use to block the current
		308	coroutine and wait for events: first you remember the current coroutine in
		309	a variable, then arrange for some callback of yours to call C<< ->ready
		310	>> on that once some event happens, and last you call C<schedule> to put
		311	yourself to sleep. Note that a lot of things can wake your coroutine up,
		312	so you need to check wether the event indeed happened, e.g. by storing the
		313	status in a variable.
		314
		315	The canonical way to wait on external events is this:
		316
		317	{
		318	# remember current coroutine
		319	my $current = $Coro::current;
		320
		321	# register a hypothetical event handler
		322	on_event_invoke sub {
		323	# wake up sleeping coroutine
		324	$current->ready;
		325	undef $current;
		326	};
		327
		328	# call schedule until event occurred.
		329	# in case we are woken up for other reasons
		330	# (current still defined), loop.
		331	Coro::schedule while $current;
		332	}
171		333
172	=item cede	334	=item cede
173		335
174	"Cede" to other processes. This function puts the current process into the	336	"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	337	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.	338	up the current "timeslice" to other coroutines of the same or higher
		339	priority. Once your coroutine gets its turn again it will automatically be
		340	resumed.
177		341
178	=cut	342	This function is often called C<yield> in other languages.
179		343
		344	=item Coro::cede_notself
		345
		346	Works like cede, but is not exported by default and will cede to I<any>
		347	coroutine, regardless of priority. This is useful sometimes to ensure
		348	progress is made.
		349
180	=item terminate	350	=item terminate [arg...]
181		351
182	Terminates the current process.	352	Terminates the current coroutine with the given status values (see L<cancel>).
183		353
184	Future versions of this function will allow result arguments.	354	=item killall
		355
		356	Kills/terminates/cancels all coroutines except the currently running
		357	one. This is useful after a fork, either in the child or the parent, as
		358	usually only one of them should inherit the running coroutines.
		359
		360	Note that while this will try to free some of the main programs resources,
		361	you cnanot free all of them, so if a coroutine that is not the main
		362	program calls this function, there will be some one-time resource leak.
185		363
186	=cut	364	=cut
187		365
188	sub terminate {	366	sub terminate {
189	$current->cancel;	367	$current->cancel (@_);
190	&schedule;	368	}
191	die; # NORETURN	369
		370	sub killall {
		371	for (Coro::State::list) {
		372	$_->cancel
		373	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		374	}
192	}	375	}
193		376
194	=back	377	=back
195		378
196	# dynamic methods
197
198	=head2 PROCESS METHODS	379	=head2 COROUTINE METHODS
199		380
200	These are the methods you can call on process objects.	381	These are the methods you can call on coroutine objects (or to create
		382	them).
201		383
202	=over 4	384	=over 4
203		385
204	=item new Coro \&sub [, @args...]	386	=item new Coro \&sub [, @args...]
205		387
206	Create a new process and return it. When the sub returns the process	388	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	389	automatically terminates as if C<terminate> with the returned values were
		390	called. To make the coroutine run you must first put it into the ready
208	the ready queue by calling the ready method.	391	queue by calling the ready method.
209		392
210	The coderef you submit MUST NOT be a closure that refers to variables	393	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.	394	coroutine environment.
212		395
213	=cut	396	=cut
214		397
215	sub _newcoro {	398	sub _run_coro {
216	terminate &{+shift};	399	terminate &{+shift};
217	}	400	}
218		401
219	sub new {	402	sub new {
220	my $class = shift;	403	my $class = shift;
221	bless {
222	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
223	}, $class;
224	}
225		404
226	=item $process->ready	405	$class->SUPER::new (\&_run_coro, @_)
		406	}
227		407
228	Put the current process into the ready queue.	408	=item $success = $coroutine->ready
229		409
230	=cut	410	Put the given coroutine into the end of its ready queue (there is one
		411	queue for each priority) and return true. If the coroutine is already in
		412	the ready queue, do nothing and return false.
231		413
232	=item $process->cancel	414	This ensures that the scheduler will resume this coroutine automatically
		415	once all the coroutines of higher priority and all coroutines of the same
		416	priority that were put into the ready queue earlier have been resumed.
233		417
234	Like C<terminate>, but terminates the specified process instead.	418	=item $is_ready = $coroutine->is_ready
		419
		420	Return wether the coroutine is currently the ready queue or not,
		421
		422	=item $coroutine->cancel (arg...)
		423
		424	Terminates the given coroutine and makes it return the given arguments as
		425	status (default: the empty list). Never returns if the coroutine is the
		426	current coroutine.
235		427
236	=cut	428	=cut
237		429
238	sub cancel {	430	sub cancel {
		431	my $self = shift;
		432	$self->{_status} = [@_];
		433
		434	if ($current == $self) {
239	push @destroy, $_[0];	435	push @destroy, $self;
240	$manager->ready;	436	$manager->ready;
241	&schedule if $current == $_[0];	437	&schedule while 1;
		438	} else {
		439	$self->_cancel;
		440	}
242	}	441	}
243		442
		443	=item $coroutine->join
		444
		445	Wait until the coroutine terminates and return any values given to the
		446	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		447	from multiple coroutines, and all will be resumed and given the status
		448	return once the C<$coroutine> terminates.
		449
		450	=cut
		451
		452	sub join {
		453	my $self = shift;
		454
		455	unless ($self->{_status}) {
		456	my $current = $current;
		457
		458	push @{$self->{_on_destroy}}, sub {
		459	$current->ready;
		460	undef $current;
		461	};
		462
		463	&schedule while $current;
		464	}
		465
		466	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		467	}
		468
		469	=item $coroutine->on_destroy (\&cb)
		470
		471	Registers a callback that is called when this coroutine gets destroyed,
		472	but before it is joined. The callback gets passed the terminate arguments,
		473	if any, and I<must not> die, under any circumstances.
		474
		475	=cut
		476
		477	sub on_destroy {
		478	my ($self, $cb) = @_;
		479
		480	push @{ $self->{_on_destroy} }, $cb;
		481	}
		482
244	=item $oldprio = $process->prio($newprio)	483	=item $oldprio = $coroutine->prio ($newprio)
245		484
246	Sets the priority of the process. Higher priority processes get run before	485	Sets (or gets, if the argument is missing) the priority of the
247	lower priority processes. Priorities are smalled signed integer (currently	486	coroutine. Higher priority coroutines get run before lower priority
		487	coroutines. Priorities are small signed integers (currently -4 .. +3),
248	-4 .. +3), that you can refer to using PRIO_xxx constants (use the import	488	that you can refer to using PRIO_xxx constants (use the import tag :prio
249	tag :prio to get then):	489	to get then):
250		490
251	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	491	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
252	3 > 1 > 0 > -1 > -3 > -4	492	3 > 1 > 0 > -1 > -3 > -4
253		493
254	# set priority to HIGH	494	# set priority to HIGH
255	current->prio(PRIO_HIGH);	495	current->prio(PRIO_HIGH);
256		496
257	The idle coroutine ($Coro::idle) always has a lower priority than any	497	The idle coroutine ($Coro::idle) always has a lower priority than any
258	existing coroutine.	498	existing coroutine.
259		499
260	Changing the priority of the current process will take effect immediately,	500	Changing the priority of the current coroutine will take effect immediately,
261	but changing the priority of processes in the ready queue (but not	501	but changing the priority of coroutines in the ready queue (but not
262	running) will only take effect after the next schedule (of that	502	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.	503	coroutine). This is a bug that will be fixed in some future version.
264		504
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)	505	=item $newprio = $coroutine->nice ($change)
274		506
275	Similar to C<prio>, but subtract the given value from the priority (i.e.	507	Similar to C<prio>, but subtract the given value from the priority (i.e.
276	higher values mean lower priority, just as in unix).	508	higher values mean lower priority, just as in unix).
277		509
278	=cut	510	=item $olddesc = $coroutine->desc ($newdesc)
279		511
280	sub nice {	512	Sets (or gets in case the argument is missing) the description for this
281	$_[0]{prio} -= $_[1];	513	coroutine. This is just a free-form string you can associate with a coroutine.
		514
		515	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
		516	can modify this member directly if you wish.
		517
		518	=item $coroutine->throw ([$scalar])
		519
		520	If C<$throw> is specified and defined, it will be thrown as an exception
		521	inside the coroutine at the next convinient point in time (usually after
		522	it gains control at the next schedule/transfer/cede). Otherwise clears the
		523	exception object.
		524
		525	The exception object will be thrown "as is" with the specified scalar in
		526	C<$@>, i.e. if it is a string, no line number or newline will be appended
		527	(unlike with C<die>).
		528
		529	This can be used as a softer means than C<cancel> to ask a coroutine to
		530	end itself, although there is no guarentee that the exception will lead to
		531	termination, and if the exception isn't caught it might well end the whole
		532	program.
		533
		534	=cut
		535
		536	sub desc {
		537	my $old = $_[0]{desc};
		538	$_[0]{desc} = $_[1] if @_ > 1;
		539	$old;
282	}	540	}
283		541
284	=back	542	=back
285		543
		544	=head2 GLOBAL FUNCTIONS
		545
		546	=over 4
		547
		548	=item Coro::nready
		549
		550	Returns the number of coroutines that are currently in the ready state,
		551	i.e. that can be switched to by calling C<schedule> directory or
		552	indirectly. The value C<0> means that the only runnable coroutine is the
		553	currently running one, so C<cede> would have no effect, and C<schedule>
		554	would cause a deadlock unless there is an idle handler that wakes up some
		555	coroutines.
		556
		557	=item my $guard = Coro::guard { ... }
		558
		559	This creates and returns a guard object. Nothing happens until the object
		560	gets destroyed, in which case the codeblock given as argument will be
		561	executed. This is useful to free locks or other resources in case of a
		562	runtime error or when the coroutine gets canceled, as in both cases the
		563	guard block will be executed. The guard object supports only one method,
		564	C<< ->cancel >>, which will keep the codeblock from being executed.
		565
		566	Example: set some flag and clear it again when the coroutine gets canceled
		567	or the function returns:
		568
		569	sub do_something {
		570	my $guard = Coro::guard { $busy = 0 };
		571	$busy = 1;
		572
		573	# do something that requires $busy to be true
		574	}
		575
		576	=cut
		577
		578	sub guard(&) {
		579	bless \(my $cb = $_[0]), "Coro::guard"
		580	}
		581
		582	sub Coro::guard::cancel {
		583	${$_[0]} = sub { };
		584	}
		585
		586	sub Coro::guard::DESTROY {
		587	${$_[0]}->();
		588	}
		589
		590
		591	=item unblock_sub { ... }
		592
		593	This utility function takes a BLOCK or code reference and "unblocks" it,
		594	returning a new coderef. Unblocking means that calling the new coderef
		595	will return immediately without blocking, returning nothing, while the
		596	original code ref will be called (with parameters) from within another
		597	coroutine.
		598
		599	The reason this function exists is that many event libraries (such as the
		600	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		601	of thread-safety). This means you must not block within event callbacks,
		602	otherwise you might suffer from crashes or worse. The only event library
		603	currently known that is safe to use without C<unblock_sub> is L<EV>.
		604
		605	This function allows your callbacks to block by executing them in another
		606	coroutine where it is safe to block. One example where blocking is handy
		607	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		608	disk, for example.
		609
		610	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		611	creating event callbacks that want to block.
		612
		613	If your handler does not plan to block (e.g. simply sends a message to
		614	another coroutine, or puts some other coroutine into the ready queue),
		615	there is no reason to use C<unblock_sub>.
		616
		617	Note that you also need to use C<unblock_sub> for any other callbacks that
		618	are indirectly executed by any C-based event loop. For example, when you
		619	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		620	provides callbacks that are the result of some event callback, then you
		621	must not block either, or use C<unblock_sub>.
		622
		623	=cut
		624
		625	our @unblock_queue;
		626
		627	# we create a special coro because we want to cede,
		628	# to reduce pressure on the coro pool (because most callbacks
		629	# return immediately and can be reused) and because we cannot cede
		630	# inside an event callback.
		631	our $unblock_scheduler = new Coro sub {
		632	while () {
		633	while (my $cb = pop @unblock_queue) {
		634	# this is an inlined copy of async_pool
		635	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		636
		637	$coro->{_invoke} = $cb;
		638	$coro->ready;
		639	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		640	}
		641	schedule; # sleep well
		642	}
		643	};
		644	$unblock_scheduler->desc ("[unblock_sub scheduler]");
		645
		646	sub unblock_sub(&) {
		647	my $cb = shift;
		648
		649	sub {
		650	unshift @unblock_queue, [$cb, @_];
		651	$unblock_scheduler->ready;
		652	}
		653	}
		654
		655	=back
		656
286	=cut	657	=cut
287		658
288	1;	659	1;
289		660
290	=head1 BUGS/LIMITATIONS	661	=head1 BUGS/LIMITATIONS
291		662
292	- you must make very sure that no coro is still active on global destruction.	663	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	664	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).	665	future to allow per-thread schedulers, but Coro::State does not yet allow
		666	this). I recommend disabling thread support and using processes, as this
		667	is much faster and uses less memory.
297		668
298	=head1 SEE ALSO	669	=head1 SEE ALSO
299		670
300	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	671	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>,	672
302	L<Coro::Handle>, L<Coro::Socket>.	673	Debugging: L<Coro::Debug>.
		674
		675	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		676
		677	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		678
		679	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		680
		681	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		682
		683	XS API: L<Coro::MakeMaker>.
		684
		685	Low level Configuration, Coroutine Environment: L<Coro::State>.
303		686
304	=head1 AUTHOR	687	=head1 AUTHOR
305		688
306	Marc Lehmann <pcg@goof.com>	689	Marc Lehmann <schmorp@schmorp.de>
307	http://www.goof.com/pcg/marc/	690	http://home.schmorp.de/
308		691
309	=cut	692	=cut
310		693

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Comparing Coro/Coro.pm (file contents): Revision 1.37 by root, Mon Sep 24 02:25:44 2001 UTC vs. Revision 1.191 by root, Sat May 31 12:10:55 2008 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.37 by root, Mon Sep 24 02:25:44 2001 UTC vs.
Revision 1.191 by root, Sat May 31 12:10:55 2008 UTC