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

Comparing Coro/Coro.pm (file contents):
Revision 1.91 by root, Fri Dec 1 02:17:37 2006 UTC vs.
Revision 1.225 by root, Wed Nov 19 15:29:57 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
35	use strict;	61	use strict qw(vars subs);
36	no warnings "uninitialized";	62	no warnings "uninitialized";
37		63
38	use Coro::State;	64	use Coro::State;
39		65
40	use base qw(Coro::State Exporter);	66	use base qw(Coro::State Exporter);
41		67
42	our $idle; # idle handler	68	our $idle; # idle handler
43	our $main; # main coroutine	69	our $main; # main coroutine
44	our $current; # current coroutine	70	our $current; # current coroutine
45		71
46	our $VERSION = '3.0';	72	our $VERSION = 5.0;
47		73
48	our @EXPORT = qw(async cede schedule terminate current);	74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
49	our %EXPORT_TAGS = (	75	our %EXPORT_TAGS = (
50	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51	);	77	);
52	our @EXPORT_OK = @{$EXPORT_TAGS{prio}};	78	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
53
54	{
55	my @async;
56	my $init;
57
58	# this way of handling attributes simply is NOT scalable ;()
59	sub import {
60	no strict 'refs';
61
62	Coro->export_to_level(1, @_);
63
64	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
65	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
66	my ($package, $ref) = (shift, shift);
67	my @attrs;
68	for (@_) {
69	if ($_ eq "Coro") {
70	push @async, $ref;
71	unless ($init++) {
72	eval q{
73	sub INIT {
74	&async(pop @async) while @async;
75	}
76	};
77	}
78	} else {
79	push @attrs, $_;
80	}
81	}
82	return $old ? $old->($package, $ref, @attrs) : @attrs;
83	};
84	}
85
86	}
87		79
88	=over 4	80	=over 4
89		81
90	=item $main	82	=item $Coro::main
91		83
92	This coroutine represents the main program.	84	This variable stores the coroutine object that represents the main
		85	program. While you cna C<ready> it and do most other things you can do to
		86	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		87	whether you are running in the main program or not.
93		88
94	=cut	89	=cut
95		90
96	$main = new Coro;	91	# $main is now being initialised by Coro::State
97		92
98	=item $current (or as function: current)	93	=item $Coro::current
99		94
100	The current coroutine (the last coroutine switched to). The initial value	95	The coroutine object representing the current coroutine (the last
		96	coroutine that the Coro scheduler switched to). The initial value is
101	is C<$main> (of course).	97	C<$Coro::main> (of course).
102		98
103	This variable is B<strictly> I<read-only>. It is provided for performance	99	This variable is B<strictly> I<read-only>. You can take copies of the
104	reasons. If performance is not essentiel you are encouraged to use the	100	value stored in it and use it as any other coroutine object, but you must
105	C<Coro::current> function instead.	101	not otherwise modify the variable itself.
106		102
107	=cut	103	=cut
108		104
109	# maybe some other module used Coro::Specific before...
110	if ($current) {
111	$main->{specific} = $current->{specific};
112	}
113
114	$current = $main;
115
116	sub current() { $current }	105	sub current() { $current } # [DEPRECATED]
117		106
118	=item $idle	107	=item $Coro::idle
119		108
120	A callback that is called whenever the scheduler finds no ready coroutines	109	This variable is mainly useful to integrate Coro into event loops. It is
121	to run. The default implementation prints "FATAL: deadlock detected" and	110	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
122	exits, because the program has no other way to continue.	111	pretty low-level functionality.
		112
		113	This variable stores a callback that is called whenever the scheduler
		114	finds no ready coroutines to run. The default implementation prints
		115	"FATAL: deadlock detected" and exits, because the program has no other way
		116	to continue.
123		117
124	This hook is overwritten by modules such as C<Coro::Timer> and	118	This hook is overwritten by modules such as C<Coro::Timer> and
125	C<Coro::Event> to wait on an external event that hopefully wake up a	119	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
126	coroutine so the scheduler can run it.	120	coroutine so the scheduler can run it.
127		121
		122	Note that the callback I<must not>, under any circumstances, block
		123	the current coroutine. Normally, this is achieved by having an "idle
		124	coroutine" that calls the event loop and then blocks again, and then
		125	readying that coroutine in the idle handler.
		126
		127	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		128	technique.
		129
128	Please note that if your callback recursively invokes perl (e.g. for event	130	Please note that if your callback recursively invokes perl (e.g. for event
129	handlers), then it must be prepared to be called recursively.	131	handlers), then it must be prepared to be called recursively itself.
130		132
131	=cut	133	=cut
132		134
133	$idle = sub {	135	$idle = sub {
134	print STDERR "FATAL: deadlock detected\n";	136	require Carp;
135	exit (51);	137	Carp::croak ("FATAL: deadlock detected");
136	};	138	};
		139
		140	sub _cancel {
		141	my ($self) = @_;
		142
		143	# free coroutine data and mark as destructed
		144	$self->_destroy
		145	or return;
		146
		147	# call all destruction callbacks
		148	$_->(@{$self->{_status}})
		149	for @{ delete $self->{_on_destroy} \|\| [] };
		150	}
137		151
138	# this coroutine is necessary because a coroutine	152	# this coroutine is necessary because a coroutine
139	# cannot destroy itself.	153	# cannot destroy itself.
140	my @destroy;	154	my @destroy;
		155	my $manager;
		156
141	my $manager; $manager = new Coro sub {	157	$manager = new Coro sub {
142	while () {	158	while () {
143	# by overwriting the state object with the manager we destroy it	159	(shift @destroy)->_cancel
144	# while still being able to schedule this coroutine (in case it has
145	# been readied multiple times. this is harmless since the manager
146	# can be called as many times as neccessary and will always
147	# remove itself from the runqueue
148	while (@destroy) {	160	while @destroy;
149	my $coro = pop @destroy;
150	$coro->{status} \|\|= [];
151	$_->ready for @{delete $coro->{join} \|\| []};
152		161
153	# the next line destroys the coro state, but keeps the
154	# process itself intact (we basically make it a zombie
155	# process that always runs the manager thread, so it's possible
156	# to transfer() to this process).
157	$coro->_clone_state_from ($manager);
158	}
159	&schedule;	162	&schedule;
160	}	163	}
161	};	164	};
162		165	$manager->{desc} = "[coro manager]";
163	# static methods. not really.	166	$manager->prio (PRIO_MAX);
164		167
165	=back	168	=back
166		169
167	=head2 STATIC METHODS	170	=head2 SIMPLE COROUTINE CREATION
168
169	Static methods are actually functions that operate on the current process only.
170		171
171	=over 4	172	=over 4
172		173
173	=item async { ... } [@args...]	174	=item async { ... } [@args...]
174		175
175	Create a new asynchronous process and return it's process object	176	Create a new coroutine and return it's coroutine object (usually
176	(usually unused). When the sub returns the new process is automatically	177	unused). The coroutine will be put into the ready queue, so
		178	it will start running automatically on the next scheduler run.
		179
		180	The first argument is a codeblock/closure that should be executed in the
		181	coroutine. When it returns argument returns the coroutine is automatically
177	terminated.	182	terminated.
178		183
179	Calling C<exit> in a coroutine will not work correctly, so do not do that.	184	The remaining arguments are passed as arguments to the closure.
180		185
181	When the coroutine dies, the program will exit, just as in the main	186	See the C<Coro::State::new> constructor for info about the coroutine
182	program.	187	environment in which coroutines are executed.
183		188
		189	Calling C<exit> in a coroutine will do the same as calling exit outside
		190	the coroutine. Likewise, when the coroutine dies, the program will exit,
		191	just as it would in the main program.
		192
		193	If you do not want that, you can provide a default C<die> handler, or
		194	simply avoid dieing (by use of C<eval>).
		195
184	# create a new coroutine that just prints its arguments	196	Example: Create a new coroutine that just prints its arguments.
		197
185	async {	198	async {
186	print "@_\n";	199	print "@_\n";
187	} 1,2,3,4;	200	} 1,2,3,4;
188		201
189	=cut	202	=cut
190		203
191	sub async(&@) {	204	sub async(&@) {
192	my $pid = new Coro @_;	205	my $coro = new Coro @_;
193	$pid->ready;	206	$coro->ready;
194	$pid	207	$coro
195	}	208	}
		209
		210	=item async_pool { ... } [@args...]
		211
		212	Similar to C<async>, but uses a coroutine pool, so you should not call
		213	terminate or join on it (although you are allowed to), and you get a
		214	coroutine that might have executed other code already (which can be good
		215	or bad :).
		216
		217	On the plus side, this function is faster than creating (and destroying)
		218	a completly new coroutine, so if you need a lot of generic coroutines in
		219	quick successsion, use C<async_pool>, not C<async>.
		220
		221	The code block is executed in an C<eval> context and a warning will be
		222	issued in case of an exception instead of terminating the program, as
		223	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		224	will not work in the expected way, unless you call terminate or cancel,
		225	which somehow defeats the purpose of pooling (but is fine in the
		226	exceptional case).
		227
		228	The priority will be reset to C<0> after each run, tracing will be
		229	disabled, the description will be reset and the default output filehandle
		230	gets restored, so you can change all these. Otherwise the coroutine will
		231	be re-used "as-is": most notably if you change other per-coroutine global
		232	stuff such as C<$/> you I<must needs> revert that change, which is most
		233	simply done by using local as in: C<< local $/ >>.
		234
		235	The idle pool size is limited to C<8> idle coroutines (this can be
		236	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		237	coros as required.
		238
		239	If you are concerned about pooled coroutines growing a lot because a
		240	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		241	{ terminate }> once per second or so to slowly replenish the pool. In
		242	addition to that, when the stacks used by a handler grows larger than 16kb
		243	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		244
		245	=cut
		246
		247	our $POOL_SIZE = 8;
		248	our $POOL_RSS = 16 * 1024;
		249	our @async_pool;
		250
		251	sub pool_handler {
		252	my $cb;
		253
		254	while () {
		255	eval {
		256	while () {
		257	_pool_1 $cb;
		258	&$cb;
		259	_pool_2 $cb;
		260	&schedule;
		261	}
		262	};
		263
		264	if ($@) {
		265	last if $@ eq "\3async_pool terminate\2\n";
		266	warn $@;
		267	}
		268	}
		269	}
		270
		271	sub async_pool(&@) {
		272	# this is also inlined into the unblock_scheduler
		273	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		274
		275	$coro->{_invoke} = [@_];
		276	$coro->ready;
		277
		278	$coro
		279	}
		280
		281	=back
		282
		283	=head2 STATIC METHODS
		284
		285	Static methods are actually functions that operate on the current coroutine.
		286
		287	=over 4
196		288
197	=item schedule	289	=item schedule
198		290
199	Calls the scheduler. Please note that the current process will not be put	291	Calls the scheduler. The scheduler will find the next coroutine that is
		292	to be run from the ready queue and switches to it. The next coroutine
		293	to be run is simply the one with the highest priority that is longest
		294	in its ready queue. If there is no coroutine ready, it will clal the
		295	C<$Coro::idle> hook.
		296
		297	Please note that the current coroutine will I<not> be put into the ready
200	into the ready queue, so calling this function usually means you will	298	queue, so calling this function usually means you will never be called
201	never be called again unless something else (e.g. an event handler) calls	299	again unless something else (e.g. an event handler) calls C<< ->ready >>,
202	ready.	300	thus waking you up.
203		301
204	The canonical way to wait on external events is this:	302	This makes C<schedule> I<the> generic method to use to block the current
		303	coroutine and wait for events: first you remember the current coroutine in
		304	a variable, then arrange for some callback of yours to call C<< ->ready
		305	>> on that once some event happens, and last you call C<schedule> to put
		306	yourself to sleep. Note that a lot of things can wake your coroutine up,
		307	so you need to check whether the event indeed happened, e.g. by storing the
		308	status in a variable.
205		309
		310	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
		311
		312	=item cede
		313
		314	"Cede" to other coroutines. This function puts the current coroutine into
		315	the ready queue and calls C<schedule>, which has the effect of giving
		316	up the current "timeslice" to other coroutines of the same or higher
		317	priority. Once your coroutine gets its turn again it will automatically be
		318	resumed.
		319
		320	This function is often called C<yield> in other languages.
		321
		322	=item Coro::cede_notself
		323
		324	Works like cede, but is not exported by default and will cede to I<any>
		325	coroutine, regardless of priority. This is useful sometimes to ensure
		326	progress is made.
		327
		328	=item terminate [arg...]
		329
		330	Terminates the current coroutine with the given status values (see L<cancel>).
		331
		332	=item killall
		333
		334	Kills/terminates/cancels all coroutines except the currently running
		335	one. This is useful after a fork, either in the child or the parent, as
		336	usually only one of them should inherit the running coroutines.
		337
		338	Note that while this will try to free some of the main programs resources,
		339	you cannot free all of them, so if a coroutine that is not the main
		340	program calls this function, there will be some one-time resource leak.
		341
		342	=cut
		343
		344	sub terminate {
		345	$current->cancel (@_);
		346	}
		347
		348	sub killall {
		349	for (Coro::State::list) {
		350	$_->cancel
		351	if $_ != $current && UNIVERSAL::isa $_, "Coro";
206	{	352	}
207	# remember current process	353	}
		354
		355	=back
		356
		357	=head2 COROUTINE METHODS
		358
		359	These are the methods you can call on coroutine objects (or to create
		360	them).
		361
		362	=over 4
		363
		364	=item new Coro \&sub [, @args...]
		365
		366	Create a new coroutine and return it. When the sub returns, the coroutine
		367	automatically terminates as if C<terminate> with the returned values were
		368	called. To make the coroutine run you must first put it into the ready
		369	queue by calling the ready method.
		370
		371	See C<async> and C<Coro::State::new> for additional info about the
		372	coroutine environment.
		373
		374	=cut
		375
		376	sub _terminate {
		377	terminate &{+shift};
		378	}
		379
		380	=item $success = $coroutine->ready
		381
		382	Put the given coroutine into the end of its ready queue (there is one
		383	queue for each priority) and return true. If the coroutine is already in
		384	the ready queue, do nothing and return false.
		385
		386	This ensures that the scheduler will resume this coroutine automatically
		387	once all the coroutines of higher priority and all coroutines of the same
		388	priority that were put into the ready queue earlier have been resumed.
		389
		390	=item $is_ready = $coroutine->is_ready
		391
		392	Return whether the coroutine is currently the ready queue or not,
		393
		394	=item $coroutine->cancel (arg...)
		395
		396	Terminates the given coroutine and makes it return the given arguments as
		397	status (default: the empty list). Never returns if the coroutine is the
		398	current coroutine.
		399
		400	=cut
		401
		402	sub cancel {
		403	my $self = shift;
		404	$self->{_status} = [@_];
		405
		406	if ($current == $self) {
		407	push @destroy, $self;
		408	$manager->ready;
		409	&schedule while 1;
		410	} else {
		411	$self->_cancel;
		412	}
		413	}
		414
		415	=item $coroutine->throw ([$scalar])
		416
		417	If C<$throw> is specified and defined, it will be thrown as an exception
		418	inside the coroutine at the next convenient point in time. Otherwise
		419	clears the exception object.
		420
		421	Coro will check for the exception each time a schedule-like-function
		422	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		423	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		424	detect this case and return early in case an exception is pending.
		425
		426	The exception object will be thrown "as is" with the specified scalar in
		427	C<$@>, i.e. if it is a string, no line number or newline will be appended
		428	(unlike with C<die>).
		429
		430	This can be used as a softer means than C<cancel> to ask a coroutine to
		431	end itself, although there is no guarantee that the exception will lead to
		432	termination, and if the exception isn't caught it might well end the whole
		433	program.
		434
		435	You might also think of C<throw> as being the moral equivalent of
		436	C<kill>ing a coroutine with a signal (in this case, a scalar).
		437
		438	=item $coroutine->join
		439
		440	Wait until the coroutine terminates and return any values given to the
		441	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		442	from multiple coroutines, and all will be resumed and given the status
		443	return once the C<$coroutine> terminates.
		444
		445	=cut
		446
		447	sub join {
		448	my $self = shift;
		449
		450	unless ($self->{_status}) {
208	my $current = $Coro::current;	451	my $current = $current;
209		452
210	# register a hypothetical event handler	453	push @{$self->{_on_destroy}}, sub {
211	on_event_invoke sub {
212	# wake up sleeping coroutine
213	$current->ready;	454	$current->ready;
214	undef $current;	455	undef $current;
215	};	456	};
216		457
217	# call schedule until event occured.
218	# in case we are woken up for other reasons
219	# (current still defined), loop.
220	Coro::schedule while $current;	458	&schedule while $current;
221	}	459	}
222		460
223	=cut
224
225	=item cede
226
227	"Cede" to other processes. This function puts the current process into the
228	ready queue and calls C<schedule>, which has the effect of giving up the
229	current "timeslice" to other coroutines of the same or higher priority.
230
231	=cut
232
233	=item terminate [arg...]
234
235	Terminates the current process with the given status values (see L<cancel>).
236
237	=cut
238
239	sub terminate {
240	$current->cancel (@_);
241	}
242
243	=back
244
245	# dynamic methods
246
247	=head2 PROCESS METHODS
248
249	These are the methods you can call on process objects.
250
251	=over 4
252
253	=item new Coro \&sub [, @args...]
254
255	Create a new process and return it. When the sub returns the process
256	automatically terminates as if C<terminate> with the returned values were
257	called. To make the process run you must first put it into the ready queue
258	by calling the ready method.
259
260	Calling C<exit> in a coroutine will not work correctly, so do not do that.
261
262	=cut
263
264	sub _new_coro {
265	terminate &{+shift};
266	}
267
268	sub new {
269	my $class = shift;
270
271	$class->SUPER::new (\&_new_coro, @_)
272	}
273
274	=item $success = $process->ready
275
276	Put the given process into the ready queue (according to it's priority)
277	and return true. If the process is already in the ready queue, do nothing
278	and return false.
279
280	=item $is_ready = $process->is_ready
281
282	Return wether the process is currently the ready queue or not,
283
284	=item $process->cancel (arg...)
285
286	Terminates the given process and makes it return the given arguments as
287	status (default: the empty list).
288
289	=cut
290
291	sub cancel {
292	my $self = shift;
293	$self->{status} = [@_];
294	push @destroy, $self;
295	$manager->ready;
296	&schedule if $current == $self;
297	}
298
299	=item $process->join
300
301	Wait until the coroutine terminates and return any values given to the
302	C<terminate> or C<cancel> functions. C<join> can be called multiple times
303	from multiple processes.
304
305	=cut
306
307	sub join {
308	my $self = shift;
309	unless ($self->{status}) {
310	push @{$self->{join}}, $current;
311	&schedule;
312	}
313	wantarray ? @{$self->{status}} : $self->{status}[0];	461	wantarray ? @{$self->{_status}} : $self->{_status}[0];
314	}	462	}
315		463
		464	=item $coroutine->on_destroy (\&cb)
		465
		466	Registers a callback that is called when this coroutine gets destroyed,
		467	but before it is joined. The callback gets passed the terminate arguments,
		468	if any, and I<must not> die, under any circumstances.
		469
		470	=cut
		471
		472	sub on_destroy {
		473	my ($self, $cb) = @_;
		474
		475	push @{ $self->{_on_destroy} }, $cb;
		476	}
		477
316	=item $oldprio = $process->prio ($newprio)	478	=item $oldprio = $coroutine->prio ($newprio)
317		479
318	Sets (or gets, if the argument is missing) the priority of the	480	Sets (or gets, if the argument is missing) the priority of the
319	process. Higher priority processes get run before lower priority	481	coroutine. Higher priority coroutines get run before lower priority
320	processes. Priorities are small signed integers (currently -4 .. +3),	482	coroutines. Priorities are small signed integers (currently -4 .. +3),
321	that you can refer to using PRIO_xxx constants (use the import tag :prio	483	that you can refer to using PRIO_xxx constants (use the import tag :prio
322	to get then):	484	to get then):
323		485
324	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	486	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
325	3 > 1 > 0 > -1 > -3 > -4	487	3 > 1 > 0 > -1 > -3 > -4
…		…
328	current->prio(PRIO_HIGH);	490	current->prio(PRIO_HIGH);
329		491
330	The idle coroutine ($Coro::idle) always has a lower priority than any	492	The idle coroutine ($Coro::idle) always has a lower priority than any
331	existing coroutine.	493	existing coroutine.
332		494
333	Changing the priority of the current process will take effect immediately,	495	Changing the priority of the current coroutine will take effect immediately,
334	but changing the priority of processes in the ready queue (but not	496	but changing the priority of coroutines in the ready queue (but not
335	running) will only take effect after the next schedule (of that	497	running) will only take effect after the next schedule (of that
336	process). This is a bug that will be fixed in some future version.	498	coroutine). This is a bug that will be fixed in some future version.
337		499
338	=item $newprio = $process->nice ($change)	500	=item $newprio = $coroutine->nice ($change)
339		501
340	Similar to C<prio>, but subtract the given value from the priority (i.e.	502	Similar to C<prio>, but subtract the given value from the priority (i.e.
341	higher values mean lower priority, just as in unix).	503	higher values mean lower priority, just as in unix).
342		504
343	=item $olddesc = $process->desc ($newdesc)	505	=item $olddesc = $coroutine->desc ($newdesc)
344		506
345	Sets (or gets in case the argument is missing) the description for this	507	Sets (or gets in case the argument is missing) the description for this
346	process. This is just a free-form string you can associate with a process.	508	coroutine. This is just a free-form string you can associate with a
		509	coroutine.
		510
		511	This method simply sets the C<< $coroutine->{desc} >> member to the given
		512	string. You can modify this member directly if you wish.
347		513
348	=cut	514	=cut
349		515
350	sub desc {	516	sub desc {
351	my $old = $_[0]{desc};	517	my $old = $_[0]{desc};
…		…
353	$old;	519	$old;
354	}	520	}
355		521
356	=back	522	=back
357		523
		524	=head2 GLOBAL FUNCTIONS
		525
		526	=over 4
		527
		528	=item Coro::nready
		529
		530	Returns the number of coroutines that are currently in the ready state,
		531	i.e. that can be switched to by calling C<schedule> directory or
		532	indirectly. The value C<0> means that the only runnable coroutine is the
		533	currently running one, so C<cede> would have no effect, and C<schedule>
		534	would cause a deadlock unless there is an idle handler that wakes up some
		535	coroutines.
		536
		537	=item my $guard = Coro::guard { ... }
		538
		539	This creates and returns a guard object. Nothing happens until the object
		540	gets destroyed, in which case the codeblock given as argument will be
		541	executed. This is useful to free locks or other resources in case of a
		542	runtime error or when the coroutine gets canceled, as in both cases the
		543	guard block will be executed. The guard object supports only one method,
		544	C<< ->cancel >>, which will keep the codeblock from being executed.
		545
		546	Example: set some flag and clear it again when the coroutine gets canceled
		547	or the function returns:
		548
		549	sub do_something {
		550	my $guard = Coro::guard { $busy = 0 };
		551	$busy = 1;
		552
		553	# do something that requires $busy to be true
		554	}
		555
		556	=cut
		557
		558	sub guard(&) {
		559	bless \(my $cb = $_[0]), "Coro::guard"
		560	}
		561
		562	sub Coro::guard::cancel {
		563	${$_[0]} = sub { };
		564	}
		565
		566	sub Coro::guard::DESTROY {
		567	${$_[0]}->();
		568	}
		569
		570
		571	=item unblock_sub { ... }
		572
		573	This utility function takes a BLOCK or code reference and "unblocks" it,
		574	returning a new coderef. Unblocking means that calling the new coderef
		575	will return immediately without blocking, returning nothing, while the
		576	original code ref will be called (with parameters) from within another
		577	coroutine.
		578
		579	The reason this function exists is that many event libraries (such as the
		580	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		581	of thread-safety). This means you must not block within event callbacks,
		582	otherwise you might suffer from crashes or worse. The only event library
		583	currently known that is safe to use without C<unblock_sub> is L<EV>.
		584
		585	This function allows your callbacks to block by executing them in another
		586	coroutine where it is safe to block. One example where blocking is handy
		587	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		588	disk, for example.
		589
		590	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		591	creating event callbacks that want to block.
		592
		593	If your handler does not plan to block (e.g. simply sends a message to
		594	another coroutine, or puts some other coroutine into the ready queue),
		595	there is no reason to use C<unblock_sub>.
		596
		597	Note that you also need to use C<unblock_sub> for any other callbacks that
		598	are indirectly executed by any C-based event loop. For example, when you
		599	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		600	provides callbacks that are the result of some event callback, then you
		601	must not block either, or use C<unblock_sub>.
		602
		603	=cut
		604
		605	our @unblock_queue;
		606
		607	# we create a special coro because we want to cede,
		608	# to reduce pressure on the coro pool (because most callbacks
		609	# return immediately and can be reused) and because we cannot cede
		610	# inside an event callback.
		611	our $unblock_scheduler = new Coro sub {
		612	while () {
		613	while (my $cb = pop @unblock_queue) {
		614	# this is an inlined copy of async_pool
		615	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		616
		617	$coro->{_invoke} = $cb;
		618	$coro->ready;
		619	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		620	}
		621	schedule; # sleep well
		622	}
		623	};
		624	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
		625
		626	sub unblock_sub(&) {
		627	my $cb = shift;
		628
		629	sub {
		630	unshift @unblock_queue, [$cb, @_];
		631	$unblock_scheduler->ready;
		632	}
		633	}
		634
		635	=item $cb = Coro::rouse_cb
		636
		637	Create and return a "rouse callback". That's a code reference that, when
		638	called, will save its arguments and notify the owner coroutine of the
		639	callback.
		640
		641	See the next function.
		642
		643	=item @args = Coro::rouse_wait [$cb]
		644
		645	Wait for the specified rouse callback (or the last one tht was created in
		646	this coroutine).
		647
		648	As soon as the callback is invoked (or when the calback was invoked before
		649	C<rouse_wait>), it will return a copy of the arguments originally passed
		650	to the rouse callback.
		651
		652	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		653
		654	=back
		655
358	=cut	656	=cut
359		657
360	1;	658	1;
361		659
		660	=head1 HOW TO WAIT FOR A CALLBACK
		661
		662	It is very common for a coroutine to wait for some callback to be
		663	called. This occurs naturally when you use coroutines in an otherwise
		664	event-based program, or when you use event-based libraries.
		665
		666	These typically register a callback for some event, and call that callback
		667	when the event occured. In a coroutine, however, you typically want to
		668	just wait for the event, simplyifying things.
		669
		670	For example C<< AnyEvent->child >> registers a callback to be called when
		671	a specific child has exited:
		672
		673	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		674
		675	But from withina coroutine, you often just want to write this:
		676
		677	my $status = wait_for_child $pid;
		678
		679	Coro offers two functions specifically designed to make this easy,
		680	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		681
		682	The first function, C<rouse_cb>, generates and returns a callback that,
		683	when invoked, will save it's arguments and notify the coroutine that
		684	created the callback.
		685
		686	The second function, C<rouse_wait>, waits for the callback to be called
		687	(by calling C<schedule> to go to sleep) and returns the arguments
		688	originally passed to the callback.
		689
		690	Using these functions, it becomes easy to write the C<wait_for_child>
		691	function mentioned above:
		692
		693	sub wait_for_child($) {
		694	my ($pid) = @_;
		695
		696	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		697
		698	my ($rpid, $rstatus) = Coro::rouse_wait;
		699	$rstatus
		700	}
		701
		702	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		703	you can roll your own, using C<schedule>:
		704
		705	sub wait_for_child($) {
		706	my ($pid) = @_;
		707
		708	# store the current coroutine in $current,
		709	# and provide result variables for the closure passed to ->child
		710	my $current = $Coro::current;
		711	my ($done, $rstatus);
		712
		713	# pass a closure to ->child
		714	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		715	$rstatus = $_[1]; # remember rstatus
		716	$done = 1; # mark $rstatus as valud
		717	});
		718
		719	# wait until the closure has been called
		720	schedule while !$done;
		721
		722	$rstatus
		723	}
		724
		725
362	=head1 BUGS/LIMITATIONS	726	=head1 BUGS/LIMITATIONS
363		727
364	- you must make very sure that no coro is still active on global	728	=over 4
365	destruction. very bad things might happen otherwise (usually segfaults).
366		729
		730	=item fork with pthread backend
		731
		732	When Coro is compiled using the pthread backend (which isn't recommended
		733	but required on many BSDs as their libcs are completely broken), then
		734	coroutines will not survive a fork. There is no known workaround except to
		735	fix your libc and use a saner backend.
		736
		737	=item perl process emulation ("threads")
		738
367	- this module is not thread-safe. You should only ever use this module	739	This module is not perl-pseudo-thread-safe. You should only ever use this
368	from the same thread (this requirement might be losened in the future	740	module from the same thread (this requirement might be removed in the
369	to allow per-thread schedulers, but Coro::State does not yet allow	741	future to allow per-thread schedulers, but Coro::State does not yet allow
370	this).	742	this). I recommend disabling thread support and using processes, as having
		743	the windows process emulation enabled under unix roughly halves perl
		744	performance, even when not used.
		745
		746	=item coroutine switching not signal safe
		747
		748	You must not switch to another coroutine from within a signal handler
		749	(only relevant with %SIG - most event libraries provide safe signals).
		750
		751	That means you I<MUST NOT> call any function that might "block" the
		752	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		753	anything that calls those. Everything else, including calling C<ready>,
		754	works.
		755
		756	=back
		757
371		758
372	=head1 SEE ALSO	759	=head1 SEE ALSO
373		760
		761	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		762
		763	Debugging: L<Coro::Debug>.
		764
374	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	765	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
375		766
376	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	767	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
377		768
378	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	769	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
379		770
380	Embedding: L<Coro:MakeMaker>	771	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		772
		773	XS API: L<Coro::MakeMaker>.
		774
		775	Low level Configuration, Coroutine Environment: L<Coro::State>.
381		776
382	=head1 AUTHOR	777	=head1 AUTHOR
383		778
384	Marc Lehmann <schmorp@schmorp.de>	779	Marc Lehmann <schmorp@schmorp.de>
385	http://home.schmorp.de/	780	http://home.schmorp.de/

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Comparing Coro/Coro.pm (file contents): Revision 1.91 by root, Fri Dec 1 02:17:37 2006 UTC vs. Revision 1.225 by root, Wed Nov 19 15:29:57 2008 UTC

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Revision 1.91 by root, Fri Dec 1 02:17:37 2006 UTC vs.
Revision 1.225 by root, Wed Nov 19 15:29:57 2008 UTC