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

Comparing Coro/Coro.pm (file contents):
Revision 1.66 by root, Thu Mar 3 17:20:31 2005 UTC vs.
Revision 1.186 by root, Sun May 25 01:32:36 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
		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.
		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
26	In this module, coroutines are defined as "callchain + lexical variables	51	In this module, coroutines are defined as "callchain + lexical variables +
27	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own	52	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
28	callchain, it's own set of lexicals and it's own set of perl's most	53	its own set of lexicals and its own set of perls most important global
29	important global variables.	54	variables (see L<Coro::State> for more configuration).
30		55
31	=cut	56	=cut
32		57
33	package Coro;	58	package Coro;
34		59
35	BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") }	60	use strict;
		61	no warnings "uninitialized";
36		62
37	use Coro::State;	63	use Coro::State;
38		64
39	use vars qw($idle $main $current);	65	use base qw(Coro::State Exporter);
40		66
41	use base Exporter;	67	our $idle; # idle handler
		68	our $main; # main coroutine
		69	our $current; # current coroutine
42		70
43	$VERSION = 1.11;	71	our $VERSION = '4.72';
44		72
45	@EXPORT = qw(async cede schedule terminate current);	73	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46	%EXPORT_TAGS = (	74	our %EXPORT_TAGS = (
47	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	75	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48	);	76	);
49	@EXPORT_OK = @{$EXPORT_TAGS{prio}};	77	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
50
51	{
52	my @async;
53	my $init;
54
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		78
82	=over 4	79	=over 4
83		80
84	=item $main	81	=item $Coro::main
85		82
86	This coroutine represents the main program.	83	This variable stores the coroutine object that represents the main
		84	program. While you cna C<ready> it and do most other things you can do to
		85	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		86	wether you are running in the main program or not.
87		87
88	=cut	88	=cut
89		89
90	$main = new Coro;	90	$main = new Coro;
91		91
92	=item $current (or as function: current)	92	=item $Coro::current
93		93
94	The current coroutine (the last coroutine switched to). The initial value is C<$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).
95		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
96	=cut	102	=cut
		103
		104	$main->{desc} = "[main::]";
97		105
98	# maybe some other module used Coro::Specific before...	106	# maybe some other module used Coro::Specific before...
99	if ($current) {
100	$main->{specific} = $current->{specific};	107	$main->{_specific} = $current->{_specific}
101	}	108	if $current;
102		109
103	$current = $main;	110	_set_current $main;
104		111
105	sub current() { $current }	112	sub current() { $current } # [DEPRECATED]
106		113
107	=item $idle	114	=item $Coro::idle
108		115
109	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
110	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.
111		119
112	=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.
113		124
114	# should be done using priorities :(	125	This hook is overwritten by modules such as C<Coro::Timer> and
115	$idle = new Coro sub {	126	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
116	print STDERR "FATAL: deadlock detected\n";	127	coroutine so the scheduler can run it.
117	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	$idle = sub {
		143	require Carp;
		144	Carp::croak ("FATAL: deadlock detected");
118	};	145	};
		146
		147	sub _cancel {
		148	my ($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	}
119		158
120	# this coroutine is necessary because a coroutine	159	# this coroutine is necessary because a coroutine
121	# cannot destroy itself.	160	# cannot destroy itself.
122	my @destroy;	161	my @destroy;
123	my $manager;	162	my $manager;
		163
124	$manager = new Coro sub {	164	$manager = new Coro sub {
125	while () {	165	while () {
126	# by overwriting the state object with the manager we destroy it	166	(shift @destroy)->_cancel
127	# while still being able to schedule this coroutine (in case it has
128	# been readied multiple times. this is harmless since the manager
129	# can be called as many times as neccessary and will always
130	# remove itself from the runqueue
131	while (@destroy) {	167	while @destroy;
132	my $coro = pop @destroy;
133	$coro->{status} \|\|= [];
134	$_->ready for @{delete $coro->{join} \|\| []};
135		168
136	# the next line destroys the _coro_state, but keeps the
137	# process itself intact (we basically make it a zombie
138	# process that always runs the manager thread, so it's possible
139	# to transfer() to this process).
140	$coro->{_coro_state} = $manager->{_coro_state};
141	}
142	&schedule;	169	&schedule;
143	}	170	}
144	};	171	};
145		172	$manager->desc ("[coro manager]");
146	# static methods. not really.	173	$manager->prio (PRIO_MAX);
147		174
148	=back	175	=back
149		176
150	=head2 STATIC METHODS	177	=head2 SIMPLE COROUTINE CREATION
151
152	Static methods are actually functions that operate on the current process only.
153		178
154	=over 4	179	=over 4
155		180
156	=item async { ... } [@args...]	181	=item async { ... } [@args...]
157		182
158	Create a new asynchronous process and return it's process object	183	Create a new coroutine and return it's coroutine object (usually
159	(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
160	terminated.	189	terminated.
161		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
162	# create a new coroutine that just prints its arguments	203	Example: Create a new coroutine that just prints its arguments.
		204
163	async {	205	async {
164	print "@_\n";	206	print "@_\n";
165	} 1,2,3,4;	207	} 1,2,3,4;
166		208
167	=cut	209	=cut
168		210
169	sub async(&@) {	211	sub async(&@) {
170	my $pid = new Coro @_;	212	my $coro = new Coro @_;
171	$manager->ready; # this ensures that the stack is cloned from the manager
172	$pid->ready;	213	$coro->ready;
173	$pid;	214	$coro
174	}	215	}
		216
		217	=item async_pool { ... } [@args...]
		218
		219	Similar to C<async>, but uses a coroutine pool, so you should not call
		220	terminate or join on it (although you are allowed to), and you get a
		221	coroutine that might have executed other code already (which can be good
		222	or bad :).
		223
		224	On the plus side, this function is faster than creating (and destroying)
		225	a completely new coroutine, so if you need a lot of generic coroutines in
		226	quick successsion, use C<async_pool>, not C<async>.
		227
		228	The code block is executed in an C<eval> context and a warning will be
		229	issued in case of an exception instead of terminating the program, as
		230	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		231	will not work in the expected way, unless you call terminate or cancel,
		232	which somehow defeats the purpose of pooling (but is fine in the
		233	exceptional case).
		234
		235	The priority will be reset to C<0> after each run, tracing will be
		236	disabled, the description will be reset and the default output filehandle
		237	gets restored, so you can change all these. Otherwise the coroutine will
		238	be re-used "as-is": most notably if you change other per-coroutine global
		239	stuff such as C<$/> 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	$coro
		284	}
		285
		286	=back
		287
		288	=head2 STATIC METHODS
		289
		290	Static methods are actually functions that operate on the current coroutine.
		291
		292	=over 4
175		293
176	=item schedule	294	=item schedule
177		295
178	Calls the scheduler. Please note that the current process will not be put	296	Calls the scheduler. The scheduler will find the next coroutine that is
		297	to be run from the ready queue and switches to it. The next coroutine
		298	to be run is simply the one with the highest priority that is longest
		299	in its ready queue. If there is no coroutine ready, it will clal the
		300	C<$Coro::idle> hook.
		301
		302	Please note that the current coroutine will I<not> be put into the ready
179	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
180	never be called again.	304	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		305	thus waking you up.
181		306
182	=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	}
183		333
184	=item cede	334	=item cede
185		335
186	"Cede" to other processes. This function puts the current process into the	336	"Cede" to other coroutines. This function puts the current coroutine into
187	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
188	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.
189		341
190	=cut	342	This function is often called C<yield> in other languages.
		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.
191		349
192	=item terminate [arg...]	350	=item terminate [arg...]
193		351
194	Terminates the current process with the given status values (see L<cancel>).	352	Terminates the current coroutine with the given status values (see L<cancel>).
		353
		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.
195		363
196	=cut	364	=cut
197		365
198	sub terminate {	366	sub terminate {
199	$current->cancel (@_);	367	$current->cancel (@_);
200	}	368	}
201		369
		370	sub killall {
		371	for (Coro::State::list) {
		372	$_->cancel
		373	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		374	}
		375	}
		376
202	=back	377	=back
203		378
204	# dynamic methods
205
206	=head2 PROCESS METHODS	379	=head2 COROUTINE METHODS
207		380
208	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).
209		383
210	=over 4	384	=over 4
211		385
212	=item new Coro \&sub [, @args...]	386	=item new Coro \&sub [, @args...]
213		387
214	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
215	automatically terminates as if C<terminate> with the returned values were	389	automatically terminates as if C<terminate> with the returned values were
216	called. To make the process run you must first put it into the ready queue	390	called. To make the coroutine run you must first put it into the ready
217	by calling the ready method.	391	queue by calling the ready method.
218		392
219	=cut	393	See C<async> and C<Coro::State::new> for additional info about the
		394	coroutine environment.
220		395
		396	=cut
		397
221	sub _newcoro {	398	sub _run_coro {
222	terminate &{+shift};	399	terminate &{+shift};
223	}	400	}
224		401
225	sub new {	402	sub new {
226	my $class = shift;	403	my $class = shift;
227	bless {
228	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229	}, $class;
230	}
231		404
232	=item $process->ready	405	$class->SUPER::new (\&_run_coro, @_)
		406	}
233		407
234	Put the given process into the ready queue.	408	=item $success = $coroutine->ready
235		409
236	=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.
237		413
		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.
		417
		418	=item $is_ready = $coroutine->is_ready
		419
		420	Return wether the coroutine is currently the ready queue or not,
		421
238	=item $process->cancel (arg...)	422	=item $coroutine->cancel (arg...)
239		423
240	Temrinates the given process and makes it return the given arguments as	424	Terminates the given coroutine and makes it return the given arguments as
241	status (default: the empty list).	425	status (default: the empty list). Never returns if the coroutine is the
		426	current coroutine.
242		427
243	=cut	428	=cut
244		429
245	sub cancel {	430	sub cancel {
246	my $self = shift;	431	my $self = shift;
247	$self->{status} = [@_];	432	$self->{_status} = [@_];
		433
		434	if ($current == $self) {
248	push @destroy, $self;	435	push @destroy, $self;
249	$manager->ready;	436	$manager->ready;
250	&schedule if $current == $self;	437	&schedule while 1;
		438	} else {
		439	$self->_cancel;
		440	}
251	}	441	}
252		442
253	=item $process->join	443	=item $coroutine->join
254		444
255	Wait until the coroutine terminates and return any values given to the	445	Wait until the coroutine terminates and return any values given to the
256	C<terminate> or C<cancel> functions. C<join> can be called multiple times	446	C<terminate> or C<cancel> functions. C<join> can be called concurrently
257	from multiple processes.	447	from multiple coroutines, and all will be resumed and given the status
		448	return once the C<$coroutine> terminates.
258		449
259	=cut	450	=cut
260		451
261	sub join {	452	sub join {
262	my $self = shift;	453	my $self = shift;
		454
263	unless ($self->{status}) {	455	unless ($self->{_status}) {
264	push @{$self->{join}}, $current;	456	my $current = $current;
265	&schedule;	457
		458	push @{$self->{_on_destroy}}, sub {
		459	$current->ready;
		460	undef $current;
		461	};
		462
		463	&schedule while $current;
266	}	464	}
		465
267	wantarray ? @{$self->{status}} : $self->{status}[0];	466	wantarray ? @{$self->{_status}} : $self->{_status}[0];
268	}	467	}
269		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
270	=item $oldprio = $process->prio($newprio)	483	=item $oldprio = $coroutine->prio ($newprio)
271		484
272	Sets (or gets, if the argument is missing) the priority of the	485	Sets (or gets, if the argument is missing) the priority of the
273	process. Higher priority processes get run before lower priority	486	coroutine. Higher priority coroutines get run before lower priority
274	processes. Priorities are small signed integers (currently -4 .. +3),	487	coroutines. Priorities are small signed integers (currently -4 .. +3),
275	that you can refer to using PRIO_xxx constants (use the import tag :prio	488	that you can refer to using PRIO_xxx constants (use the import tag :prio
276	to get then):	489	to get then):
277		490
278	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
279	3 > 1 > 0 > -1 > -3 > -4	492	3 > 1 > 0 > -1 > -3 > -4
…		…
282	current->prio(PRIO_HIGH);	495	current->prio(PRIO_HIGH);
283		496
284	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
285	existing coroutine.	498	existing coroutine.
286		499
287	Changing the priority of the current process will take effect immediately,	500	Changing the priority of the current coroutine will take effect immediately,
288	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
289	running) will only take effect after the next schedule (of that	502	running) will only take effect after the next schedule (of that
290	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.
291		504
292	=cut
293
294	sub prio {
295	my $old = $_[0]{prio};
296	$_[0]{prio} = $_[1] if @_ > 1;
297	$old;
298	}
299
300	=item $newprio = $process->nice($change)	505	=item $newprio = $coroutine->nice ($change)
301		506
302	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.
303	higher values mean lower priority, just as in unix).	508	higher values mean lower priority, just as in unix).
304		509
305	=cut
306
307	sub nice {
308	$_[0]{prio} -= $_[1];
309	}
310
311	=item $olddesc = $process->desc($newdesc)	510	=item $olddesc = $coroutine->desc ($newdesc)
312		511
313	Sets (or gets in case the argument is missing) the description for this	512	Sets (or gets in case the argument is missing) the description for this
314	process. This is just a free-form string you can associate with a process.	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.
315		533
316	=cut	534	=cut
317		535
318	sub desc {	536	sub desc {
319	my $old = $_[0]{desc};	537	my $old = $_[0]{desc};
…		…
321	$old;	539	$old;
322	}	540	}
323		541
324	=back	542	=back
325		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
326	=cut	657	=cut
327		658
328	1;	659	1;
329		660
330	=head1 BUGS/LIMITATIONS	661	=head1 BUGS/LIMITATIONS
331		662
332	- you must make very sure that no coro is still active on global
333	destruction. very bad things might happen otherwise (usually segfaults).
334
335	- this module is not thread-safe. You should only ever use this module	663	This module is not perl-pseudo-thread-safe. You should only ever use this
336	from the same thread (this requirement might be losened in the future	664	module from the same thread (this requirement might be removed in the
337	to allow per-thread schedulers, but Coro::State does not yet allow	665	future to allow per-thread schedulers, but Coro::State does not yet allow
338	this).	666	this). I recommend disabling thread support and using processes, as this
		667	is much faster and uses less memory.
339		668
340	=head1 SEE ALSO	669	=head1 SEE ALSO
341		670
342	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>.
343	L<Coro::Signal>, L<Coro::State>, L<Coro::Timer>, L<Coro::Event>,	672
344	L<Coro::Handle>, L<Coro::RWLock>, 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>.
345		686
346	=head1 AUTHOR	687	=head1 AUTHOR
347		688
348	Marc Lehmann <schmorp@schmorp.de>	689	Marc Lehmann <schmorp@schmorp.de>
349	http://home.schmorp.de/	690	http://home.schmorp.de/

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Revision 1.186 by root, Sun May 25 01:32:36 2008 UTC