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

Comparing Coro/Coro.pm (file contents):
Revision 1.52 by root, Tue May 27 00:26:34 2003 UTC vs.
Revision 1.198 by root, Sun Sep 21 01:23:26 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
		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
		61	use strict;
35	no warnings qw(uninitialized);	62	no warnings "uninitialized";
36		63
37	use Coro::State;	64	use Coro::State;
38		65
39	use base Exporter;	66	use base qw(Coro::State Exporter);
40		67
41	$VERSION = 0.652;	68	our $idle; # idle handler
		69	our $main; # main coroutine
		70	our $current; # current coroutine
42		71
		72	our $VERSION = 4.746;
		73
43	@EXPORT = qw(async cede schedule terminate current);	74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44	%EXPORT_TAGS = (	75	our %EXPORT_TAGS = (
45	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46	);	77	);
47	@EXPORT_OK = @{$EXPORT_TAGS{prio}};	78	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
48
49	{
50	my @async;
51	my $init;
52
53	# this way of handling attributes simply is NOT scalable ;()
54	sub import {
55	Coro->export_to_level(1, @_);
56	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
57	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
58	my ($package, $ref) = (shift, shift);
59	my @attrs;
60	for (@_) {
61	if ($_ eq "Coro") {
62	push @async, $ref;
63	unless ($init++) {
64	eval q{
65	sub INIT {
66	&async(pop @async) while @async;
67	}
68	};
69	}
70	} else {
71	push @attrs, $_;
72	}
73	}
74	return $old ? $old->($package, $ref, @attrs) : @attrs;
75	};
76	}
77
78	}
79		79
80	=over 4	80	=over 4
81		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;
121	my $manager;	163	my $manager;
		164
122	$manager = new Coro sub {	165	$manager = new Coro sub {
123	while() {	166	while () {
124	# by overwriting the state object with the manager we destroy it	167	(shift @destroy)->_cancel
125	# while still being able to schedule this coroutine (in case it has
126	# been readied multiple times. this is harmless since the manager
127	# can be called as many times as neccessary and will always
128	# remove itself from the runqueue
129	while (@destroy) {	168	while @destroy;
130	my $coro = pop @destroy;	169
131	$coro->{status} \|\|= [];
132	$_->ready for @{delete $coro->{join} \|\| []};
133	$coro->{_coro_state} = $manager->{_coro_state};
134	}
135	&schedule;	170	&schedule;
136	}	171	}
137	};	172	};
138		173	$manager->desc ("[coro manager]");
139	# static methods. not really.	174	$manager->prio (PRIO_MAX);
140		175
141	=back	176	=back
142		177
143	=head2 STATIC METHODS	178	=head2 SIMPLE COROUTINE CREATION
144
145	Static methods are actually functions that operate on the current process only.
146		179
147	=over 4	180	=over 4
148		181
149	=item async { ... } [@args...]	182	=item async { ... } [@args...]
150		183
151	Create a new asynchronous process and return it's process object	184	Create a new coroutine and return it's coroutine object (usually
152	(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
153	terminated.	190	terminated.
154		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
155	# create a new coroutine that just prints its arguments	204	Example: Create a new coroutine that just prints its arguments.
		205
156	async {	206	async {
157	print "@_\n";	207	print "@_\n";
158	} 1,2,3,4;	208	} 1,2,3,4;
159		209
160	The coderef you submit MUST NOT be a closure that refers to variables
161	in an outer scope. This does NOT work. Pass arguments into it instead.
162
163	=cut	210	=cut
164		211
165	sub async(&@) {	212	sub async(&@) {
166	my $pid = new Coro @_;	213	my $coro = new Coro @_;
167	$manager->ready; # this ensures that the stack is cloned from the manager
168	$pid->ready;	214	$coro->ready;
169	$pid;	215	$coro
170	}	216	}
		217
		218	=item async_pool { ... } [@args...]
		219
		220	Similar to C<async>, but uses a coroutine pool, so you should not call
		221	terminate or join on it (although you are allowed to), and you get a
		222	coroutine that might have executed other code already (which can be good
		223	or bad :).
		224
		225	On the plus side, this function is faster than creating (and destroying)
		226	a completely new coroutine, so if you need a lot of generic coroutines in
		227	quick successsion, use C<async_pool>, not C<async>.
		228
		229	The code block is executed in an C<eval> context and a warning will be
		230	issued in case of an exception instead of terminating the program, as
		231	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		232	will not work in the expected way, unless you call terminate or cancel,
		233	which somehow defeats the purpose of pooling (but is fine in the
		234	exceptional case).
		235
		236	The priority will be reset to C<0> after each run, tracing will be
		237	disabled, the description will be reset and the default output filehandle
		238	gets restored, so you can change all these. Otherwise the coroutine will
		239	be re-used "as-is": most notably if you change other per-coroutine global
		240	stuff such as C<$/> you I<must needs> to revert that change, which is most
		241	simply done by using local as in: C< local $/ >.
		242
		243	The pool size is limited to C<8> idle coroutines (this can be adjusted by
		244	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		245	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	$coro
		287	}
		288
		289	=back
		290
		291	=head2 STATIC METHODS
		292
		293	Static methods are actually functions that operate on the current coroutine.
		294
		295	=over 4
171		296
172	=item schedule	297	=item schedule
173		298
174	Calls the scheduler. Please note that the current process will not be put	299	Calls the scheduler. The scheduler will find the next coroutine that is
		300	to be run from the ready queue and switches to it. The next coroutine
		301	to be run is simply the one with the highest priority that is longest
		302	in its ready queue. If there is no coroutine ready, it will clal the
		303	C<$Coro::idle> hook.
		304
		305	Please note that the current coroutine will I<not> be put into the ready
175	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
176	never be called again.	307	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		308	thus waking you up.
177		309
178	=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	}
179		336
180	=item cede	337	=item cede
181		338
182	"Cede" to other processes. This function puts the current process into the	339	"Cede" to other coroutines. This function puts the current coroutine into
183	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
184	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.
185		344
186	=cut	345	This function is often called C<yield> in other languages.
		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.
187		352
188	=item terminate [arg...]	353	=item terminate [arg...]
189		354
190	Terminates the current process.	355	Terminates the current coroutine with the given status values (see L<cancel>).
191		356
192	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.
193		366
194	=cut	367	=cut
195		368
196	sub terminate {	369	sub terminate {
197	$current->{status} = [@_];
198	$current->cancel;	370	$current->cancel (@_);
199	&schedule;	371	}
200	die; # NORETURN	372
		373	sub killall {
		374	for (Coro::State::list) {
		375	$_->cancel
		376	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		377	}
201	}	378	}
202		379
203	=back	380	=back
204		381
205	# dynamic methods
206
207	=head2 PROCESS METHODS	382	=head2 COROUTINE METHODS
208		383
209	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).
210		386
211	=over 4	387	=over 4
212		388
213	=item new Coro \&sub [, @args...]	389	=item new Coro \&sub [, @args...]
214		390
215	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
216	automatically terminates as if C<terminate> with the returned values were	392	automatically terminates as if C<terminate> with the returned values were
217	called. To make the process run you must first put it into the ready queue	393	called. To make the coroutine run you must first put it into the ready
218	by calling the ready method.	394	queue by calling the ready method.
219		395
220	=cut	396	See C<async> and C<Coro::State::new> for additional info about the
		397	coroutine environment.
221		398
		399	=cut
		400
222	sub _newcoro {	401	sub _run_coro {
223	terminate &{+shift};	402	terminate &{+shift};
224	}	403	}
225		404
226	sub new {	405	sub new {
227	my $class = shift;	406	my $class = shift;
228	bless {
229	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
230	}, $class;
231	}
232		407
233	=item $process->ready	408	$class->SUPER::new (\&_run_coro, @_)
		409	}
234		410
235	Put the given process into the ready queue.	411	=item $success = $coroutine->ready
236		412
237	=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.
238		416
239	=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.
240		420
241	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.
242		430
243	=cut	431	=cut
244		432
245	sub cancel {	433	sub cancel {
		434	my $self = shift;
		435	$self->{_status} = [@_];
		436
		437	if ($current == $self) {
246	push @destroy, $_[0];	438	push @destroy, $self;
247	$manager->ready;	439	$manager->ready;
248	&schedule if $current == $_[0];	440	&schedule while 1;
		441	} else {
		442	$self->_cancel;
		443	}
249	}	444	}
250		445
251	=item $process->join	446	=item $coroutine->join
252		447
253	Wait until the coroutine terminates and return any values given to the	448	Wait until the coroutine terminates and return any values given to the
254	C<terminate> function. C<join> can be called multiple times from multiple	449	C<terminate> or C<cancel> functions. C<join> can be called concurrently
255	processes.	450	from multiple coroutines, and all will be resumed and given the status
		451	return once the C<$coroutine> terminates.
256		452
257	=cut	453	=cut
258		454
259	sub join {	455	sub join {
260	my $self = shift;	456	my $self = shift;
		457
261	unless ($self->{status}) {	458	unless ($self->{_status}) {
262	push @{$self->{join}}, $current;	459	my $current = $current;
263	&schedule;	460
		461	push @{$self->{_on_destroy}}, sub {
		462	$current->ready;
		463	undef $current;
		464	};
		465
		466	&schedule while $current;
264	}	467	}
		468
265	wantarray ? @{$self->{status}} : $self->{status}[0];	469	wantarray ? @{$self->{_status}} : $self->{_status}[0];
266	}	470	}
267		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
268	=item $oldprio = $process->prio($newprio)	486	=item $oldprio = $coroutine->prio ($newprio)
269		487
270	Sets (or gets, if the argument is missing) the priority of the	488	Sets (or gets, if the argument is missing) the priority of the
271	process. Higher priority processes get run before lower priority	489	coroutine. Higher priority coroutines get run before lower priority
272	processes. Priorities are small signed integers (currently -4 .. +3),	490	coroutines. Priorities are small signed integers (currently -4 .. +3),
273	that you can refer to using PRIO_xxx constants (use the import tag :prio	491	that you can refer to using PRIO_xxx constants (use the import tag :prio
274	to get then):	492	to get then):
275		493
276	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
277	3 > 1 > 0 > -1 > -3 > -4	495	3 > 1 > 0 > -1 > -3 > -4
…		…
280	current->prio(PRIO_HIGH);	498	current->prio(PRIO_HIGH);
281		499
282	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
283	existing coroutine.	501	existing coroutine.
284		502
285	Changing the priority of the current process will take effect immediately,	503	Changing the priority of the current coroutine will take effect immediately,
286	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
287	running) will only take effect after the next schedule (of that	505	running) will only take effect after the next schedule (of that
288	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.
289		507
290	=cut
291
292	sub prio {
293	my $old = $_[0]{prio};
294	$_[0]{prio} = $_[1] if @_ > 1;
295	$old;
296	}
297
298	=item $newprio = $process->nice($change)	508	=item $newprio = $coroutine->nice ($change)
299		509
300	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.
301	higher values mean lower priority, just as in unix).	511	higher values mean lower priority, just as in unix).
302		512
303	=cut
304
305	sub nice {
306	$_[0]{prio} -= $_[1];
307	}
308
309	=item $olddesc = $process->desc($newdesc)	513	=item $olddesc = $coroutine->desc ($newdesc)
310		514
311	Sets (or gets in case the argument is missing) the description for this	515	Sets (or gets in case the argument is missing) the description for this
312	process. This is just a free-form string you can associate with a process.	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.
313		536
314	=cut	537	=cut
315		538
316	sub desc {	539	sub desc {
317	my $old = $_[0]{desc};	540	my $old = $_[0]{desc};
…		…
319	$old;	542	$old;
320	}	543	}
321		544
322	=back	545	=back
323		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
324	=cut	660	=cut
325		661
326	1;	662	1;
327		663
328	=head1 BUGS/LIMITATIONS	664	=head1 BUGS/LIMITATIONS
329		665
330	- you must make very sure that no coro is still active on global
331	destruction. very bad things might happen otherwise (usually segfaults
332	or "panic: top_env").
333
334	- this module is not thread-safe. You should only ever use this module	666	This module is not perl-pseudo-thread-safe. You should only ever use this
335	from the same thread (this requirement might be losened in the future	667	module from the same thread (this requirement might be removed in the
336	to allow per-thread schedulers, but Coro::State does not yet allow	668	future to allow per-thread schedulers, but Coro::State does not yet allow
337	this).	669	this). I recommend disabling thread support and using processes, as this
		670	is much faster and uses less memory.
338		671
339	=head1 SEE ALSO	672	=head1 SEE ALSO
340		673
341	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>.
342	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,	675
343	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>.
344		689
345	=head1 AUTHOR	690	=head1 AUTHOR
346		691
347	Marc Lehmann <pcg@goof.com>	692	Marc Lehmann <schmorp@schmorp.de>
348	http://www.goof.com/pcg/marc/	693	http://home.schmorp.de/
349		694
350	=cut	695	=cut
351		696

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Revision 1.198 by root, Sun Sep 21 01:23:26 2008 UTC