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

Comparing Coro/Coro.pm (file contents):
Revision 1.128 by root, Wed Sep 19 21:39:15 2007 UTC vs.
Revision 1.252 by root, Thu Apr 16 20:07:21 2009 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - coroutine process abstraction	3	Coro - the only real threads in perl
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 coroutine like this:	16	cede; # yield to coro
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	31	For a tutorial-style introduction, please read the L<Coro::Intro>
24	to threads but don't run in parallel at the same time even on SMP	32	manpage. This manpage mainly contains reference information.
25	machines. The specific flavor of coroutine used in this module also
26	guarantees you that it will not switch between coroutines unless
27	necessary, at easily-identified points in your program, so locking and
28	parallel access are rarely an issue, making coroutine programming much
29	safer than threads programming.
30		33
31	(Perl, however, does not natively support real threads but instead does a	34	This module collection manages continuations in general, most often in
32	very slow and memory-intensive emulation of processes using threads. This	35	the form of cooperative threads (also called coros, or simply "coro"
33	is a performance win on Windows machines, and a loss everywhere else).	36	in the documentation). They are similar to kernel threads but don't (in
		37	general) run in parallel at the same time even on SMP machines. The
		38	specific flavor of thread offered by this module also guarantees you that
		39	it will not switch between threads unless necessary, at easily-identified
		40	points in your program, so locking and parallel access are rarely an
		41	issue, making thread programming much safer and easier than using other
		42	thread models.
34		43
		44	Unlike the so-called "Perl threads" (which are not actually real threads
		45	but only the windows process emulation ported to unix, and as such act
		46	as processes), Coro provides a full shared address space, which makes
		47	communication between threads very easy. And Coro's threads are fast,
		48	too: disabling the Windows process emulation code in your perl and using
		49	Coro can easily result in a two to four times speed increase for your
		50	programs. A parallel matrix multiplication benchmark runs over 300 times
		51	faster on a single core than perl's pseudo-threads on a quad core using
		52	all four cores.
		53
		54	Coro achieves that by supporting multiple running interpreters that share
		55	data, which is especially useful to code pseudo-parallel processes and
		56	for event-based programming, such as multiple HTTP-GET requests running
		57	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		58	into an event-based environment.
		59
35	In this module, coroutines are defined as "callchain + lexical variables +	60	In this module, a thread is defined as "callchain + lexical variables +
36	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	61	some package variables + C stack), that is, a thread has its own callchain,
37	its own set of lexicals and its own set of perls most important global	62	its own set of lexicals and its own set of perls most important global
38	variables.	63	variables (see L<Coro::State> for more configuration and background info).
		64
		65	See also the C<SEE ALSO> section at the end of this document - the Coro
		66	module family is quite large.
39		67
40	=cut	68	=cut
41		69
42	package Coro;	70	package Coro;
43		71
44	use strict;	72	use strict qw(vars subs);
45	no warnings "uninitialized";	73	no warnings "uninitialized";
46		74
		75	use Guard ();
		76
47	use Coro::State;	77	use Coro::State;
48		78
49	use base qw(Coro::State Exporter);	79	use base qw(Coro::State Exporter);
50		80
51	our $idle; # idle handler	81	our $idle; # idle handler
52	our $main; # main coroutine	82	our $main; # main coro
53	our $current; # current coroutine	83	our $current; # current coro
54		84
55	our $VERSION = '3.7';	85	our $VERSION = 5.131;
56		86
57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	87	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
58	our %EXPORT_TAGS = (	88	our %EXPORT_TAGS = (
59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	89	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60	);	90	);
61	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	91	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
62		92
63	{	93	=head1 GLOBAL VARIABLES
64	my @async;
65	my $init;
66
67	# this way of handling attributes simply is NOT scalable ;()
68	sub import {
69	no strict 'refs';
70
71	Coro->export_to_level (1, @_);
72
73	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
74	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
75	my ($package, $ref) = (shift, shift);
76	my @attrs;
77	for (@_) {
78	if ($_ eq "Coro") {
79	push @async, $ref;
80	unless ($init++) {
81	eval q{
82	sub INIT {
83	&async(pop @async) while @async;
84	}
85	};
86	}
87	} else {
88	push @attrs, $_;
89	}
90	}
91	return $old ? $old->($package, $ref, @attrs) : @attrs;
92	};
93	}
94
95	}
96		94
97	=over 4	95	=over 4
98		96
99	=item $main	97	=item $Coro::main
100		98
101	This coroutine represents the main program.	99	This variable stores the Coro object that represents the main
		100	program. While you cna C<ready> it and do most other things you can do to
		101	coro, it is mainly useful to compare again C<$Coro::current>, to see
		102	whether you are running in the main program or not.
102		103
103	=cut	104	=cut
104		105
105	$main = new Coro;	106	# $main is now being initialised by Coro::State
106		107
107	=item $current (or as function: current)	108	=item $Coro::current
108		109
109	The current coroutine (the last coroutine switched to). The initial value	110	The Coro object representing the current coro (the last
		111	coro that the Coro scheduler switched to). The initial value is
110	is C<$main> (of course).	112	C<$Coro::main> (of course).
111		113
112	This variable is B<strictly> I<read-only>. It is provided for performance	114	This variable is B<strictly> I<read-only>. You can take copies of the
113	reasons. If performance is not essential you are encouraged to use the	115	value stored in it and use it as any other Coro object, but you must
114	C<Coro::current> function instead.	116	not otherwise modify the variable itself.
115		117
116	=cut	118	=cut
117		119
118	# maybe some other module used Coro::Specific before...
119	$main->{specific} = $current->{specific}
120	if $current;
121
122	_set_current $main;
123
124	sub current() { $current }	120	sub current() { $current } # [DEPRECATED]
125		121
126	=item $idle	122	=item $Coro::idle
127		123
		124	This variable is mainly useful to integrate Coro into event loops. It is
		125	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		126	pretty low-level functionality.
		127
		128	This variable stores either a Coro object or a callback.
		129
128	A callback that is called whenever the scheduler finds no ready coroutines	130	If it is a callback, the it is called whenever the scheduler finds no
129	to run. The default implementation prints "FATAL: deadlock detected" and	131	ready coros to run. The default implementation prints "FATAL:
130	exits, because the program has no other way to continue.	132	deadlock detected" and exits, because the program has no other way to
		133	continue.
131		134
		135	If it is a coro object, then this object will be readied (without
		136	invoking any ready hooks, however) when the scheduler finds no other ready
		137	coros to run.
		138
132	This hook is overwritten by modules such as C<Coro::Timer> and	139	This hook is overwritten by modules such as C<Coro::EV> and
133	C<Coro::Event> to wait on an external event that hopefully wake up a	140	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
134	coroutine so the scheduler can run it.	141	coro so the scheduler can run it.
		142
		143	Note that the callback I<must not>, under any circumstances, block
		144	the current coro. Normally, this is achieved by having an "idle
		145	coro" that calls the event loop and then blocks again, and then
		146	readying that coro in the idle handler, or by simply placing the idle
		147	coro in this variable.
		148
		149	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		150	technique.
135		151
136	Please note that if your callback recursively invokes perl (e.g. for event	152	Please note that if your callback recursively invokes perl (e.g. for event
137	handlers), then it must be prepared to be called recursively.	153	handlers), then it must be prepared to be called recursively itself.
138		154
139	=cut	155	=cut
140		156
141	$idle = sub {	157	$idle = sub {
142	require Carp;	158	require Carp;
143	Carp::croak ("FATAL: deadlock detected");	159	Carp::croak ("FATAL: deadlock detected");
144	};	160	};
145		161
146	sub _cancel {
147	my ($self) = @_;
148
149	# free coroutine data and mark as destructed
150	$self->_destroy
151	or return;
152
153	# call all destruction callbacks
154	$_->(@{$self->{status}})
155	for @{(delete $self->{destroy_cb}) \|\| []};
156	}
157
158	# this coroutine is necessary because a coroutine	162	# this coro is necessary because a coro
159	# cannot destroy itself.	163	# cannot destroy itself.
160	my @destroy;	164	our @destroy;
161	my $manager;	165	our $manager;
162		166
163	$manager = new Coro sub {	167	$manager = new Coro sub {
164	while () {	168	while () {
165	(shift @destroy)->_cancel	169	Coro::State::cancel shift @destroy
166	while @destroy;	170	while @destroy;
167		171
168	&schedule;	172	&schedule;
169	}	173	}
170	};	174	};
171		175	$manager->{desc} = "[coro manager]";
172	$manager->prio (PRIO_MAX);	176	$manager->prio (PRIO_MAX);
173		177
174	# static methods. not really.
175
176	=back	178	=back
177		179
178	=head2 STATIC METHODS	180	=head1 SIMPLE CORO CREATION
179
180	Static methods are actually functions that operate on the current coroutine only.
181		181
182	=over 4	182	=over 4
183		183
184	=item async { ... } [@args...]	184	=item async { ... } [@args...]
185		185
186	Create a new asynchronous coroutine and return it's coroutine object	186	Create a new coro and return its Coro object (usually
187	(usually unused). When the sub returns the new coroutine is automatically	187	unused). The coro will be put into the ready queue, so
		188	it will start running automatically on the next scheduler run.
		189
		190	The first argument is a codeblock/closure that should be executed in the
		191	coro. When it returns argument returns the coro is automatically
188	terminated.	192	terminated.
189		193
		194	The remaining arguments are passed as arguments to the closure.
		195
		196	See the C<Coro::State::new> constructor for info about the coro
		197	environment in which coro are executed.
		198
190	Calling C<exit> in a coroutine will do the same as calling exit outside	199	Calling C<exit> in a coro will do the same as calling exit outside
191	the coroutine. Likewise, when the coroutine dies, the program will exit,	200	the coro. Likewise, when the coro dies, the program will exit,
192	just as it would in the main program.	201	just as it would in the main program.
193		202
		203	If you do not want that, you can provide a default C<die> handler, or
		204	simply avoid dieing (by use of C<eval>).
		205
194	# create a new coroutine that just prints its arguments	206	Example: Create a new coro that just prints its arguments.
		207
195	async {	208	async {
196	print "@_\n";	209	print "@_\n";
197	} 1,2,3,4;	210	} 1,2,3,4;
198		211
199	=cut	212	=cut
204	$coro	217	$coro
205	}	218	}
206		219
207	=item async_pool { ... } [@args...]	220	=item async_pool { ... } [@args...]
208		221
209	Similar to C<async>, but uses a coroutine pool, so you should not call	222	Similar to C<async>, but uses a coro pool, so you should not call
210	terminate or join (although you are allowed to), and you get a coroutine	223	terminate or join on it (although you are allowed to), and you get a
211	that might have executed other code already (which can be good or bad :).	224	coro that might have executed other code already (which can be good
		225	or bad :).
212		226
		227	On the plus side, this function is about twice as fast as creating (and
		228	destroying) a completely new coro, so if you need a lot of generic
		229	coros in quick successsion, use C<async_pool>, not C<async>.
		230
213	Also, the block is executed in an C<eval> context and a warning will be	231	The code block is executed in an C<eval> context and a warning will be
214	issued in case of an exception instead of terminating the program, as	232	issued in case of an exception instead of terminating the program, as
215	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>	233	C<async> does. As the coro is being reused, stuff like C<on_destroy>
216	will not work in the expected way, unless you call terminate or cancel,	234	will not work in the expected way, unless you call terminate or cancel,
217	which somehow defeats the purpose of pooling.	235	which somehow defeats the purpose of pooling (but is fine in the
		236	exceptional case).
218		237
219	The priority will be reset to C<0> after each job, otherwise the coroutine	238	The priority will be reset to C<0> after each run, tracing will be
220	will be re-used "as-is".	239	disabled, the description will be reset and the default output filehandle
		240	gets restored, so you can change all these. Otherwise the coro will
		241	be re-used "as-is": most notably if you change other per-coro global
		242	stuff such as C<$/> you I<must needs> revert that change, which is most
		243	simply done by using local as in: C<< local $/ >>.
221		244
222	The pool size is limited to 8 idle coroutines (this can be adjusted by	245	The idle pool size is limited to C<8> idle coros (this can be
223	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as	246	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
224	required.	247	coros as required.
225		248
226	If you are concerned about pooled coroutines growing a lot because a	249	If you are concerned about pooled coros growing a lot because a
227	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {	250	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
228	terminate }> once per second or so to slowly replenish the pool.	251	{ terminate }> once per second or so to slowly replenish the pool. In
		252	addition to that, when the stacks used by a handler grows larger than 32kb
		253	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
229		254
230	=cut	255	=cut
231		256
232	our $POOL_SIZE = 8;	257	our $POOL_SIZE = 8;
		258	our $POOL_RSS = 32 * 1024;
233	our @pool;	259	our @async_pool;
234		260
235	sub pool_handler {	261	sub pool_handler {
236	while () {	262	while () {
237	eval {	263	eval {
238	my ($cb, @arg) = @{ delete $current->{_invoke} or return };	264	&{&_pool_handler} while 1;
239	$cb->(@arg);
240	};	265	};
		266
241	warn $@ if $@;	267	warn $@ if $@;
242
243	last if @pool >= $POOL_SIZE;
244	push @pool, $current;
245
246	$current->save (Coro::State::SAVE_DEF);
247	$current->prio (0);
248	schedule;
249	}	268	}
250	}	269	}
251		270
252	sub async_pool(&@) {	271	=back
253	# this is also inlined into the unlock_scheduler	272
254	my $coro = (pop @pool) \|\| do {	273	=head1 STATIC METHODS
255	my $coro = new Coro \&pool_handler;	274
256	$coro->{desc} = "async_pool";	275	Static methods are actually functions that implicitly operate on the
257	$coro	276	current coro.
		277
		278	=over 4
		279
		280	=item schedule
		281
		282	Calls the scheduler. The scheduler will find the next coro that is
		283	to be run from the ready queue and switches to it. The next coro
		284	to be run is simply the one with the highest priority that is longest
		285	in its ready queue. If there is no coro ready, it will clal the
		286	C<$Coro::idle> hook.
		287
		288	Please note that the current coro will I<not> be put into the ready
		289	queue, so calling this function usually means you will never be called
		290	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		291	thus waking you up.
		292
		293	This makes C<schedule> I<the> generic method to use to block the current
		294	coro and wait for events: first you remember the current coro in
		295	a variable, then arrange for some callback of yours to call C<< ->ready
		296	>> on that once some event happens, and last you call C<schedule> to put
		297	yourself to sleep. Note that a lot of things can wake your coro up,
		298	so you need to check whether the event indeed happened, e.g. by storing the
		299	status in a variable.
		300
		301	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
		302
		303	=item cede
		304
		305	"Cede" to other coros. This function puts the current coro into
		306	the ready queue and calls C<schedule>, which has the effect of giving
		307	up the current "timeslice" to other coros of the same or higher
		308	priority. Once your coro gets its turn again it will automatically be
		309	resumed.
		310
		311	This function is often called C<yield> in other languages.
		312
		313	=item Coro::cede_notself
		314
		315	Works like cede, but is not exported by default and will cede to I<any>
		316	coro, regardless of priority. This is useful sometimes to ensure
		317	progress is made.
		318
		319	=item terminate [arg...]
		320
		321	Terminates the current coro with the given status values (see L<cancel>).
		322
		323	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		324
		325	These function install enter and leave winders in the current scope. The
		326	enter block will be executed when on_enter is called and whenever the
		327	current coro is re-entered by the scheduler, while the leave block is
		328	executed whenever the current coro is blocked by the scheduler, and
		329	also when the containing scope is exited (by whatever means, be it exit,
		330	die, last etc.).
		331
		332	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		333	BLOCKs>. That means: do not even think about calling C<die> without an
		334	eval, and do not even think of entering the scheduler in any way.
		335
		336	Since both BLOCKs are tied to the current scope, they will automatically
		337	be removed when the current scope exits.
		338
		339	These functions implement the same concept as C<dynamic-wind> in scheme
		340	does, and are useful when you want to localise some resource to a specific
		341	coro.
		342
		343	They slow down coro switching considerably for coros that use
		344	them (But coro switching is still reasonably fast if the handlers are
		345	fast).
		346
		347	These functions are best understood by an example: The following function
		348	will change the current timezone to "Antarctica/South_Pole", which
		349	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		350	which remember/change the current timezone and restore the previous
		351	value, respectively, the timezone is only changed for the coro that
		352	installed those handlers.
		353
		354	use POSIX qw(tzset);
		355
		356	async {
		357	my $old_tz; # store outside TZ value here
		358
		359	Coro::on_enter {
		360	$old_tz = $ENV{TZ}; # remember the old value
		361
		362	$ENV{TZ} = "Antarctica/South_Pole";
		363	tzset; # enable new value
		364	};
		365
		366	Coro::on_leave {
		367	$ENV{TZ} = $old_tz;
		368	tzset; # restore old value
		369	};
		370
		371	# at this place, the timezone is Antarctica/South_Pole,
		372	# without disturbing the TZ of any other coro.
258	};	373	};
259		374
260	$coro->{_invoke} = [@_];	375	This can be used to localise about any resource (locale, uid, current
261	$coro->ready;	376	working directory etc.) to a block, despite the existance of other
		377	coros.
262		378
263	$coro	379	=item killall
264	}
265		380
266	=item schedule	381	Kills/terminates/cancels all coros except the currently running one.
267		382
268	Calls the scheduler. Please note that the current coroutine will not be put	383	Note that while this will try to free some of the main interpreter
269	into the ready queue, so calling this function usually means you will	384	resources if the calling coro isn't the main coro, but one
270	never be called again unless something else (e.g. an event handler) calls	385	cannot free all of them, so if a coro that is not the main coro
271	ready.	386	calls this function, there will be some one-time resource leak.
272		387
273	The canonical way to wait on external events is this:	388	=cut
274		389
		390	sub killall {
		391	for (Coro::State::list) {
		392	$_->cancel
		393	if $_ != $current && UNIVERSAL::isa $_, "Coro";
275	{	394	}
276	# remember current coroutine	395	}
		396
		397	=back
		398
		399	=head1 CORO OBJECT METHODS
		400
		401	These are the methods you can call on coro objects (or to create
		402	them).
		403
		404	=over 4
		405
		406	=item new Coro \&sub [, @args...]
		407
		408	Create a new coro and return it. When the sub returns, the coro
		409	automatically terminates as if C<terminate> with the returned values were
		410	called. To make the coro run you must first put it into the ready
		411	queue by calling the ready method.
		412
		413	See C<async> and C<Coro::State::new> for additional info about the
		414	coro environment.
		415
		416	=cut
		417
		418	sub _coro_run {
		419	terminate &{+shift};
		420	}
		421
		422	=item $success = $coro->ready
		423
		424	Put the given coro into the end of its ready queue (there is one
		425	queue for each priority) and return true. If the coro is already in
		426	the ready queue, do nothing and return false.
		427
		428	This ensures that the scheduler will resume this coro automatically
		429	once all the coro of higher priority and all coro of the same
		430	priority that were put into the ready queue earlier have been resumed.
		431
		432	=item $coro->suspend
		433
		434	Suspends the specified coro. A suspended coro works just like any other
		435	coro, except that the scheduler will not select a suspended coro for
		436	execution.
		437
		438	Suspending a coro can be useful when you want to keep the coro from
		439	running, but you don't want to destroy it, or when you want to temporarily
		440	freeze a coro (e.g. for debugging) to resume it later.
		441
		442	A scenario for the former would be to suspend all (other) coros after a
		443	fork and keep them alive, so their destructors aren't called, but new
		444	coros can be created.
		445
		446	=item $coro->resume
		447
		448	If the specified coro was suspended, it will be resumed. Note that when
		449	the coro was in the ready queue when it was suspended, it might have been
		450	unreadied by the scheduler, so an activation might have been lost.
		451
		452	To avoid this, it is best to put a suspended coro into the ready queue
		453	unconditionally, as every synchronisation mechanism must protect itself
		454	against spurious wakeups, and the one in the Coro family certainly do
		455	that.
		456
		457	=item $is_ready = $coro->is_ready
		458
		459	Returns true iff the Coro object is in the ready queue. Unless the Coro
		460	object gets destroyed, it will eventually be scheduled by the scheduler.
		461
		462	=item $is_running = $coro->is_running
		463
		464	Returns true iff the Coro object is currently running. Only one Coro object
		465	can ever be in the running state (but it currently is possible to have
		466	multiple running Coro::States).
		467
		468	=item $is_suspended = $coro->is_suspended
		469
		470	Returns true iff this Coro object has been suspended. Suspended Coros will
		471	not ever be scheduled.
		472
		473	=item $coro->cancel (arg...)
		474
		475	Terminates the given Coro and makes it return the given arguments as
		476	status (default: the empty list). Never returns if the Coro is the
		477	current Coro.
		478
		479	=cut
		480
		481	sub cancel {
		482	my $self = shift;
		483
		484	if ($current == $self) {
		485	terminate @_;
		486	} else {
		487	$self->{_status} = [@_];
		488	Coro::State::cancel $self;
		489	}
		490	}
		491
		492	=item $coro->schedule_to
		493
		494	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		495	of continuing with the next coro from the ready queue, always switch to
		496	the given coro object (regardless of priority etc.). The readyness
		497	state of that coro isn't changed.
		498
		499	This is an advanced method for special cases - I'd love to hear about any
		500	uses for this one.
		501
		502	=item $coro->cede_to
		503
		504	Like C<schedule_to>, but puts the current coro into the ready
		505	queue. This has the effect of temporarily switching to the given
		506	coro, and continuing some time later.
		507
		508	This is an advanced method for special cases - I'd love to hear about any
		509	uses for this one.
		510
		511	=item $coro->throw ([$scalar])
		512
		513	If C<$throw> is specified and defined, it will be thrown as an exception
		514	inside the coro at the next convenient point in time. Otherwise
		515	clears the exception object.
		516
		517	Coro will check for the exception each time a schedule-like-function
		518	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		519	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		520	detect this case and return early in case an exception is pending.
		521
		522	The exception object will be thrown "as is" with the specified scalar in
		523	C<$@>, i.e. if it is a string, no line number or newline will be appended
		524	(unlike with C<die>).
		525
		526	This can be used as a softer means than C<cancel> to ask a coro to
		527	end itself, although there is no guarantee that the exception will lead to
		528	termination, and if the exception isn't caught it might well end the whole
		529	program.
		530
		531	You might also think of C<throw> as being the moral equivalent of
		532	C<kill>ing a coro with a signal (in this case, a scalar).
		533
		534	=item $coro->join
		535
		536	Wait until the coro terminates and return any values given to the
		537	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		538	from multiple coro, and all will be resumed and given the status
		539	return once the C<$coro> terminates.
		540
		541	=cut
		542
		543	sub join {
		544	my $self = shift;
		545
		546	unless ($self->{_status}) {
277	my $current = $Coro::current;	547	my $current = $current;
278		548
279	# register a hypothetical event handler	549	push @{$self->{_on_destroy}}, sub {
280	on_event_invoke sub {
281	# wake up sleeping coroutine
282	$current->ready;	550	$current->ready;
283	undef $current;	551	undef $current;
284	};	552	};
285		553
286	# call schedule until event occurred.
287	# in case we are woken up for other reasons
288	# (current still defined), loop.
289	Coro::schedule while $current;
290	}
291
292	=item cede
293
294	"Cede" to other coroutines. This function puts the current coroutine into the
295	ready queue and calls C<schedule>, which has the effect of giving up the
296	current "timeslice" to other coroutines of the same or higher priority.
297
298	Returns true if at least one coroutine switch has happened.
299
300	=item Coro::cede_notself
301
302	Works like cede, but is not exported by default and will cede to any
303	coroutine, regardless of priority, once.
304
305	Returns true if at least one coroutine switch has happened.
306
307	=item terminate [arg...]
308
309	Terminates the current coroutine with the given status values (see L<cancel>).
310
311	=cut
312
313	sub terminate {
314	$current->cancel (@_);
315	}
316
317	=back
318
319	# dynamic methods
320
321	=head2 COROUTINE METHODS
322
323	These are the methods you can call on coroutine objects.
324
325	=over 4
326
327	=item new Coro \&sub [, @args...]
328
329	Create a new coroutine and return it. When the sub returns the coroutine
330	automatically terminates as if C<terminate> with the returned values were
331	called. To make the coroutine run you must first put it into the ready queue
332	by calling the ready method.
333
334	See C<async> for additional discussion.
335
336	=cut
337
338	sub _run_coro {
339	terminate &{+shift};
340	}
341
342	sub new {
343	my $class = shift;
344
345	$class->SUPER::new (\&_run_coro, @_)
346	}
347
348	=item $success = $coroutine->ready
349
350	Put the given coroutine into the ready queue (according to it's priority)
351	and return true. If the coroutine is already in the ready queue, do nothing
352	and return false.
353
354	=item $is_ready = $coroutine->is_ready
355
356	Return wether the coroutine is currently the ready queue or not,
357
358	=item $coroutine->cancel (arg...)
359
360	Terminates the given coroutine and makes it return the given arguments as
361	status (default: the empty list). Never returns if the coroutine is the
362	current coroutine.
363
364	=cut
365
366	sub cancel {
367	my $self = shift;
368	$self->{status} = [@_];
369
370	if ($current == $self) {
371	push @destroy, $self;
372	$manager->ready;
373	&schedule while 1;
374	} else {
375	$self->_cancel;
376	}
377	}
378
379	=item $coroutine->join
380
381	Wait until the coroutine terminates and return any values given to the
382	C<terminate> or C<cancel> functions. C<join> can be called multiple times
383	from multiple coroutine.
384
385	=cut
386
387	sub join {
388	my $self = shift;
389
390	unless ($self->{status}) {
391	my $current = $current;
392
393	push @{$self->{destroy_cb}}, sub {
394	$current->ready;
395	undef $current;
396	};
397
398	&schedule while $current;	554	&schedule while $current;
399	}	555	}
400		556
401	wantarray ? @{$self->{status}} : $self->{status}[0];	557	wantarray ? @{$self->{_status}} : $self->{_status}[0];
402	}	558	}
403		559
404	=item $coroutine->on_destroy (\&cb)	560	=item $coro->on_destroy (\&cb)
405		561
406	Registers a callback that is called when this coroutine gets destroyed,	562	Registers a callback that is called when this coro gets destroyed,
407	but before it is joined. The callback gets passed the terminate arguments,	563	but before it is joined. The callback gets passed the terminate arguments,
408	if any.	564	if any, and I<must not> die, under any circumstances.
409		565
410	=cut	566	=cut
411		567
412	sub on_destroy {	568	sub on_destroy {
413	my ($self, $cb) = @_;	569	my ($self, $cb) = @_;
414		570
415	push @{ $self->{destroy_cb} }, $cb;	571	push @{ $self->{_on_destroy} }, $cb;
416	}	572	}
417		573
418	=item $oldprio = $coroutine->prio ($newprio)	574	=item $oldprio = $coro->prio ($newprio)
419		575
420	Sets (or gets, if the argument is missing) the priority of the	576	Sets (or gets, if the argument is missing) the priority of the
421	coroutine. Higher priority coroutines get run before lower priority	577	coro. Higher priority coro get run before lower priority
422	coroutines. Priorities are small signed integers (currently -4 .. +3),	578	coro. Priorities are small signed integers (currently -4 .. +3),
423	that you can refer to using PRIO_xxx constants (use the import tag :prio	579	that you can refer to using PRIO_xxx constants (use the import tag :prio
424	to get then):	580	to get then):
425		581
426	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	582	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
427	3 > 1 > 0 > -1 > -3 > -4	583	3 > 1 > 0 > -1 > -3 > -4
428		584
429	# set priority to HIGH	585	# set priority to HIGH
430	current->prio(PRIO_HIGH);	586	current->prio (PRIO_HIGH);
431		587
432	The idle coroutine ($Coro::idle) always has a lower priority than any	588	The idle coro ($Coro::idle) always has a lower priority than any
433	existing coroutine.	589	existing coro.
434		590
435	Changing the priority of the current coroutine will take effect immediately,	591	Changing the priority of the current coro will take effect immediately,
436	but changing the priority of coroutines in the ready queue (but not	592	but changing the priority of coro in the ready queue (but not
437	running) will only take effect after the next schedule (of that	593	running) will only take effect after the next schedule (of that
438	coroutine). This is a bug that will be fixed in some future version.	594	coro). This is a bug that will be fixed in some future version.
439		595
440	=item $newprio = $coroutine->nice ($change)	596	=item $newprio = $coro->nice ($change)
441		597
442	Similar to C<prio>, but subtract the given value from the priority (i.e.	598	Similar to C<prio>, but subtract the given value from the priority (i.e.
443	higher values mean lower priority, just as in unix).	599	higher values mean lower priority, just as in unix).
444		600
445	=item $olddesc = $coroutine->desc ($newdesc)	601	=item $olddesc = $coro->desc ($newdesc)
446		602
447	Sets (or gets in case the argument is missing) the description for this	603	Sets (or gets in case the argument is missing) the description for this
448	coroutine. This is just a free-form string you can associate with a coroutine.	604	coro. This is just a free-form string you can associate with a
		605	coro.
		606
		607	This method simply sets the C<< $coro->{desc} >> member to the given
		608	string. You can modify this member directly if you wish.
449		609
450	=cut	610	=cut
451		611
452	sub desc {	612	sub desc {
453	my $old = $_[0]{desc};	613	my $old = $_[0]{desc};
454	$_[0]{desc} = $_[1] if @_ > 1;	614	$_[0]{desc} = $_[1] if @_ > 1;
455	$old;	615	$old;
456	}	616	}
457		617
		618	sub transfer {
		619	require Carp;
		620	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		621	}
		622
458	=back	623	=back
459		624
460	=head2 GLOBAL FUNCTIONS	625	=head1 GLOBAL FUNCTIONS
461		626
462	=over 4	627	=over 4
463		628
464	=item Coro::nready	629	=item Coro::nready
465		630
466	Returns the number of coroutines that are currently in the ready state,	631	Returns the number of coro that are currently in the ready state,
467	i.e. that can be switched to. The value C<0> means that the only runnable	632	i.e. that can be switched to by calling C<schedule> directory or
		633	indirectly. The value C<0> means that the only runnable coro is the
468	coroutine is the currently running one, so C<cede> would have no effect,	634	currently running one, so C<cede> would have no effect, and C<schedule>
469	and C<schedule> would cause a deadlock unless there is an idle handler	635	would cause a deadlock unless there is an idle handler that wakes up some
470	that wakes up some coroutines.	636	coro.
471		637
472	=item my $guard = Coro::guard { ... }	638	=item my $guard = Coro::guard { ... }
473		639
474	This creates and returns a guard object. Nothing happens until the object	640	This function still exists, but is deprecated. Please use the
475	gets destroyed, in which case the codeblock given as argument will be	641	C<Guard::guard> function instead.
476	executed. This is useful to free locks or other resources in case of a
477	runtime error or when the coroutine gets canceled, as in both cases the
478	guard block will be executed. The guard object supports only one method,
479	C<< ->cancel >>, which will keep the codeblock from being executed.
480		642
481	Example: set some flag and clear it again when the coroutine gets canceled
482	or the function returns:
483
484	sub do_something {
485	my $guard = Coro::guard { $busy = 0 };
486	$busy = 1;
487
488	# do something that requires $busy to be true
489	}
490
491	=cut	643	=cut
492		644
493	sub guard(&) {	645	BEGIN { *guard = \&Guard::guard }
494	bless \(my $cb = $_[0]), "Coro::guard"
495	}
496
497	sub Coro::guard::cancel {
498	${$_[0]} = sub { };
499	}
500
501	sub Coro::guard::DESTROY {
502	${$_[0]}->();
503	}
504
505		646
506	=item unblock_sub { ... }	647	=item unblock_sub { ... }
507		648
508	This utility function takes a BLOCK or code reference and "unblocks" it,	649	This utility function takes a BLOCK or code reference and "unblocks" it,
509	returning the new coderef. This means that the new coderef will return	650	returning a new coderef. Unblocking means that calling the new coderef
510	immediately without blocking, returning nothing, while the original code	651	will return immediately without blocking, returning nothing, while the
511	ref will be called (with parameters) from within its own coroutine.	652	original code ref will be called (with parameters) from within another
		653	coro.
512		654
513	The reason this function exists is that many event libraries (such as the	655	The reason this function exists is that many event libraries (such as the
514	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	656	venerable L<Event\|Event> module) are not thread-safe (a weaker form
515	of thread-safety). This means you must not block within event callbacks,	657	of reentrancy). This means you must not block within event callbacks,
516	otherwise you might suffer from crashes or worse.	658	otherwise you might suffer from crashes or worse. The only event library
		659	currently known that is safe to use without C<unblock_sub> is L<EV>.
517		660
518	This function allows your callbacks to block by executing them in another	661	This function allows your callbacks to block by executing them in another
519	coroutine where it is safe to block. One example where blocking is handy	662	coro where it is safe to block. One example where blocking is handy
520	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	663	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
521	disk.	664	disk, for example.
522		665
523	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	666	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
524	creating event callbacks that want to block.	667	creating event callbacks that want to block.
		668
		669	If your handler does not plan to block (e.g. simply sends a message to
		670	another coro, or puts some other coro into the ready queue), there is
		671	no reason to use C<unblock_sub>.
		672
		673	Note that you also need to use C<unblock_sub> for any other callbacks that
		674	are indirectly executed by any C-based event loop. For example, when you
		675	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		676	provides callbacks that are the result of some event callback, then you
		677	must not block either, or use C<unblock_sub>.
525		678
526	=cut	679	=cut
527		680
528	our @unblock_queue;	681	our @unblock_queue;
529		682
530	# we create a special coro because we want to cede,	683	# we create a special coro because we want to cede,
531	# to reduce pressure on the coro pool (because most callbacks	684	# to reduce pressure on the coro pool (because most callbacks
532	# return immediately and can be reused) and because we cannot cede	685	# return immediately and can be reused) and because we cannot cede
533	# inside an event callback.	686	# inside an event callback.
534	our $unblock_scheduler = async {	687	our $unblock_scheduler = new Coro sub {
535	while () {	688	while () {
536	while (my $cb = pop @unblock_queue) {	689	while (my $cb = pop @unblock_queue) {
537	# this is an inlined copy of async_pool	690	&async_pool (@$cb);
538	my $coro = (pop @pool or new Coro \&pool_handler);
539		691
540	$coro->{_invoke} = $cb;
541	$coro->ready;
542	cede; # for short-lived callbacks, this reduces pressure on the coro pool	692	# for short-lived callbacks, this reduces pressure on the coro pool
		693	# as the chance is very high that the async_poll coro will be back
		694	# in the idle state when cede returns
		695	cede;
543	}	696	}
544	schedule; # sleep well	697	schedule; # sleep well
545	}	698	}
546	};	699	};
		700	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
547		701
548	sub unblock_sub(&) {	702	sub unblock_sub(&) {
549	my $cb = shift;	703	my $cb = shift;
550		704
551	sub {	705	sub {
552	unshift @unblock_queue, [$cb, @_];	706	unshift @unblock_queue, [$cb, @_];
553	$unblock_scheduler->ready;	707	$unblock_scheduler->ready;
554	}	708	}
555	}	709	}
556		710
		711	=item $cb = Coro::rouse_cb
		712
		713	Create and return a "rouse callback". That's a code reference that,
		714	when called, will remember a copy of its arguments and notify the owner
		715	coro of the callback.
		716
		717	See the next function.
		718
		719	=item @args = Coro::rouse_wait [$cb]
		720
		721	Wait for the specified rouse callback (or the last one that was created in
		722	this coro).
		723
		724	As soon as the callback is invoked (or when the callback was invoked
		725	before C<rouse_wait>), it will return the arguments originally passed to
		726	the rouse callback.
		727
		728	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		729
557	=back	730	=back
558		731
559	=cut	732	=cut
560		733
561	1;	734	1;
562		735
		736	=head1 HOW TO WAIT FOR A CALLBACK
		737
		738	It is very common for a coro to wait for some callback to be
		739	called. This occurs naturally when you use coro in an otherwise
		740	event-based program, or when you use event-based libraries.
		741
		742	These typically register a callback for some event, and call that callback
		743	when the event occured. In a coro, however, you typically want to
		744	just wait for the event, simplyifying things.
		745
		746	For example C<< AnyEvent->child >> registers a callback to be called when
		747	a specific child has exited:
		748
		749	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		750
		751	But from within a coro, you often just want to write this:
		752
		753	my $status = wait_for_child $pid;
		754
		755	Coro offers two functions specifically designed to make this easy,
		756	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		757
		758	The first function, C<rouse_cb>, generates and returns a callback that,
		759	when invoked, will save its arguments and notify the coro that
		760	created the callback.
		761
		762	The second function, C<rouse_wait>, waits for the callback to be called
		763	(by calling C<schedule> to go to sleep) and returns the arguments
		764	originally passed to the callback.
		765
		766	Using these functions, it becomes easy to write the C<wait_for_child>
		767	function mentioned above:
		768
		769	sub wait_for_child($) {
		770	my ($pid) = @_;
		771
		772	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		773
		774	my ($rpid, $rstatus) = Coro::rouse_wait;
		775	$rstatus
		776	}
		777
		778	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		779	you can roll your own, using C<schedule>:
		780
		781	sub wait_for_child($) {
		782	my ($pid) = @_;
		783
		784	# store the current coro in $current,
		785	# and provide result variables for the closure passed to ->child
		786	my $current = $Coro::current;
		787	my ($done, $rstatus);
		788
		789	# pass a closure to ->child
		790	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		791	$rstatus = $_[1]; # remember rstatus
		792	$done = 1; # mark $rstatus as valud
		793	});
		794
		795	# wait until the closure has been called
		796	schedule while !$done;
		797
		798	$rstatus
		799	}
		800
		801
563	=head1 BUGS/LIMITATIONS	802	=head1 BUGS/LIMITATIONS
564		803
565	- you must make very sure that no coro is still active on global	804	=over 4
566	destruction. very bad things might happen otherwise (usually segfaults).
567		805
		806	=item fork with pthread backend
		807
		808	When Coro is compiled using the pthread backend (which isn't recommended
		809	but required on many BSDs as their libcs are completely broken), then
		810	coro will not survive a fork. There is no known workaround except to
		811	fix your libc and use a saner backend.
		812
		813	=item perl process emulation ("threads")
		814
568	- this module is not thread-safe. You should only ever use this module	815	This module is not perl-pseudo-thread-safe. You should only ever use this
569	from the same thread (this requirement might be loosened in the future	816	module from the first thread (this requirement might be removed in the
570	to allow per-thread schedulers, but Coro::State does not yet allow	817	future to allow per-thread schedulers, but Coro::State does not yet allow
571	this).	818	this). I recommend disabling thread support and using processes, as having
		819	the windows process emulation enabled under unix roughly halves perl
		820	performance, even when not used.
		821
		822	=item coro switching is not signal safe
		823
		824	You must not switch to another coro from within a signal handler
		825	(only relevant with %SIG - most event libraries provide safe signals).
		826
		827	That means you I<MUST NOT> call any function that might "block" the
		828	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		829	anything that calls those. Everything else, including calling C<ready>,
		830	works.
		831
		832	=back
		833
572		834
573	=head1 SEE ALSO	835	=head1 SEE ALSO
574		836
		837	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		838
		839	Debugging: L<Coro::Debug>.
		840
575	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	841	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
576		842
577	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	843	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		844	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
578		845
579	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	846	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
580		847
581	Embedding: L<Coro:MakeMaker>	848	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		849	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		850	L<Coro::Select>.
		851
		852	XS API: L<Coro::MakeMaker>.
		853
		854	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
582		855
583	=head1 AUTHOR	856	=head1 AUTHOR
584		857
585	Marc Lehmann <schmorp@schmorp.de>	858	Marc Lehmann <schmorp@schmorp.de>
586	http://home.schmorp.de/	859	http://home.schmorp.de/

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Comparing Coro/Coro.pm (file contents): Revision 1.128 by root, Wed Sep 19 21:39:15 2007 UTC vs. Revision 1.252 by root, Thu Apr 16 20:07:21 2009 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.128 by root, Wed Sep 19 21:39:15 2007 UTC vs.
Revision 1.252 by root, Thu Apr 16 20:07:21 2009 UTC