[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 1.239 by root, Mon Nov 24 07:55:28 2008 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 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	For a tutorial-style introduction, please read the L<Coro::Intro>
24	threads but don't run in parallel.	32	manpage. This manpage mainly contains reference information.
25		33
		34	This module collection manages continuations in general, most often
		35	in the form of cooperative threads (also called coroutines in the
		36	documentation). They are similar to kernel threads but don't (in general)
		37	run in parallel at the same time even on SMP machines. The specific flavor
		38	of thread offered by this module also guarantees you that it will not
		39	switch between threads unless necessary, at easily-identified points in
		40	your program, so locking and parallel access are rarely an issue, making
		41	thread programming much safer and easier than using other thread models.
		42
		43	Unlike the so-called "Perl threads" (which are not actually real threads
		44	but only the windows process emulation ported to unix), Coro provides a
		45	full shared address space, which makes communication between threads
		46	very easy. And threads are fast, too: disabling the Windows process
		47	emulation code in your perl and using Coro can easily result in a two to
		48	four times speed increase for your programs.
		49
		50	Coro achieves that by supporting multiple running interpreters that share
		51	data, which is especially useful to code pseudo-parallel processes and
		52	for event-based programming, such as multiple HTTP-GET requests running
		53	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		54	into an event-based environment.
		55
26	In this module, coroutines are defined as "callchain + lexical variables	56	In this module, a thread is defined as "callchain + lexical variables +
27	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own	57	@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,
28	callchain, it's own set of lexicals and it's own set of perl's most	58	its own set of lexicals and its own set of perls most important global
29	important global variables.	59	variables (see L<Coro::State> for more configuration and background info).
		60
		61	See also the C<SEE ALSO> section at the end of this document - the Coro
		62	module family is quite large.
30		63
31	=cut	64	=cut
32		65
33	package Coro;	66	package Coro;
34		67
35	BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") }	68	use strict qw(vars subs);
		69	no warnings "uninitialized";
36		70
37	use Coro::State;	71	use Coro::State;
38		72
39	use vars qw($idle $main $current);	73	use base qw(Coro::State Exporter);
40		74
41	use base Exporter;	75	our $idle; # idle handler
		76	our $main; # main coroutine
		77	our $current; # current coroutine
42		78
43	$VERSION = 1.11;	79	our $VERSION = 5.1;
44		80
45	@EXPORT = qw(async cede schedule terminate current);	81	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46	%EXPORT_TAGS = (	82	our %EXPORT_TAGS = (
47	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	83	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48	);	84	);
49	@EXPORT_OK = @{$EXPORT_TAGS{prio}};	85	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
50		86
51	{	87	=head1 GLOBAL VARIABLES
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		88
82	=over 4	89	=over 4
83		90
84	=item $main	91	=item $Coro::main
85		92
86	This coroutine represents the main program.	93	This variable stores the coroutine object that represents the main
		94	program. While you cna C<ready> it and do most other things you can do to
		95	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		96	whether you are running in the main program or not.
87		97
88	=cut	98	=cut
89		99
90	$main = new Coro;	100	# $main is now being initialised by Coro::State
91		101
92	=item $current (or as function: current)	102	=item $Coro::current
93		103
94	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	104	The coroutine object representing the current coroutine (the last
		105	coroutine that the Coro scheduler switched to). The initial value is
		106	C<$Coro::main> (of course).
95		107
96	=cut	108	This variable is B<strictly> I<read-only>. You can take copies of the
		109	value stored in it and use it as any other coroutine object, but you must
		110	not otherwise modify the variable itself.
97		111
98	# maybe some other module used Coro::Specific before...	112	=cut
99	if ($current) {
100	$main->{specific} = $current->{specific};
101	}
102		113
103	$current = $main;
104
105	sub current() { $current }	114	sub current() { $current } # [DEPRECATED]
106		115
107	=item $idle	116	=item $Coro::idle
108		117
109	The coroutine to switch to when no other coroutine is running. The default	118	This variable is mainly useful to integrate Coro into event loops. It is
110	implementation prints "FATAL: deadlock detected" and exits.	119	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		120	pretty low-level functionality.
111		121
112	=cut	122	This variable stores either a coroutine or a callback.
113		123
114	# should be done using priorities :(	124	If it is a callback, the it is called whenever the scheduler finds no
115	$idle = new Coro sub {	125	ready coroutines to run. The default implementation prints "FATAL:
116	print STDERR "FATAL: deadlock detected\n";	126	deadlock detected" and exits, because the program has no other way to
117	exit(51);	127	continue.
		128
		129	If it is a coroutine object, then this object will be readied (without
		130	invoking any ready hooks, however) when the scheduler finds no other ready
		131	coroutines to run.
		132
		133	This hook is overwritten by modules such as C<Coro::EV> and
		134	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
		135	coroutine so the scheduler can run it.
		136
		137	Note that the callback I<must not>, under any circumstances, block
		138	the current coroutine. Normally, this is achieved by having an "idle
		139	coroutine" that calls the event loop and then blocks again, and then
		140	readying that coroutine in the idle handler, or by simply placing the idle
		141	coroutine in this variable.
		142
		143	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		144	technique.
		145
		146	Please note that if your callback recursively invokes perl (e.g. for event
		147	handlers), then it must be prepared to be called recursively itself.
		148
		149	=cut
		150
		151	$idle = sub {
		152	require Carp;
		153	Carp::croak ("FATAL: deadlock detected");
118	};	154	};
119		155
120	# this coroutine is necessary because a coroutine	156	# this coroutine is necessary because a coroutine
121	# cannot destroy itself.	157	# cannot destroy itself.
122	my @destroy;	158	our @destroy;
123	my $manager;	159	our $manager;
		160
124	$manager = new Coro sub {	161	$manager = new Coro sub {
125	while () {	162	while () {
126	# by overwriting the state object with the manager we destroy it	163	Coro::_cancel shift @destroy
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) {	164	while @destroy;
132	my $coro = pop @destroy;
133	$coro->{status} \|\|= [];
134	$_->ready for @{delete $coro->{join} \|\| []};
135		165
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;	166	&schedule;
143	}	167	}
144	};	168	};
145		169	$manager->{desc} = "[coro manager]";
146	# static methods. not really.	170	$manager->prio (PRIO_MAX);
147		171
148	=back	172	=back
149		173
150	=head2 STATIC METHODS	174	=head1 SIMPLE COROUTINE CREATION
151
152	Static methods are actually functions that operate on the current process only.
153		175
154	=over 4	176	=over 4
155		177
156	=item async { ... } [@args...]	178	=item async { ... } [@args...]
157		179
158	Create a new asynchronous process and return it's process object	180	Create a new coroutine and return it's coroutine object (usually
159	(usually unused). When the sub returns the new process is automatically	181	unused). The coroutine will be put into the ready queue, so
		182	it will start running automatically on the next scheduler run.
		183
		184	The first argument is a codeblock/closure that should be executed in the
		185	coroutine. When it returns argument returns the coroutine is automatically
160	terminated.	186	terminated.
161		187
		188	The remaining arguments are passed as arguments to the closure.
		189
		190	See the C<Coro::State::new> constructor for info about the coroutine
		191	environment in which coroutines are executed.
		192
		193	Calling C<exit> in a coroutine will do the same as calling exit outside
		194	the coroutine. Likewise, when the coroutine dies, the program will exit,
		195	just as it would in the main program.
		196
		197	If you do not want that, you can provide a default C<die> handler, or
		198	simply avoid dieing (by use of C<eval>).
		199
162	# create a new coroutine that just prints its arguments	200	Example: Create a new coroutine that just prints its arguments.
		201
163	async {	202	async {
164	print "@_\n";	203	print "@_\n";
165	} 1,2,3,4;	204	} 1,2,3,4;
166		205
167	=cut	206	=cut
168		207
169	sub async(&@) {	208	sub async(&@) {
170	my $pid = new Coro @_;	209	my $coro = new Coro @_;
171	$manager->ready; # this ensures that the stack is cloned from the manager
172	$pid->ready;	210	$coro->ready;
173	$pid;	211	$coro
174	}	212	}
		213
		214	=item async_pool { ... } [@args...]
		215
		216	Similar to C<async>, but uses a coroutine pool, so you should not call
		217	terminate or join on it (although you are allowed to), and you get a
		218	coroutine that might have executed other code already (which can be good
		219	or bad :).
		220
		221	On the plus side, this function is about twice as fast as creating (and
		222	destroying) a completely new coroutine, so if you need a lot of generic
		223	coroutines in quick successsion, use C<async_pool>, not C<async>.
		224
		225	The code block is executed in an C<eval> context and a warning will be
		226	issued in case of an exception instead of terminating the program, as
		227	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		228	will not work in the expected way, unless you call terminate or cancel,
		229	which somehow defeats the purpose of pooling (but is fine in the
		230	exceptional case).
		231
		232	The priority will be reset to C<0> after each run, tracing will be
		233	disabled, the description will be reset and the default output filehandle
		234	gets restored, so you can change all these. Otherwise the coroutine will
		235	be re-used "as-is": most notably if you change other per-coroutine global
		236	stuff such as C<$/> you I<must needs> revert that change, which is most
		237	simply done by using local as in: C<< local $/ >>.
		238
		239	The idle pool size is limited to C<8> idle coroutines (this can be
		240	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		241	coros as required.
		242
		243	If you are concerned about pooled coroutines growing a lot because a
		244	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		245	{ terminate }> once per second or so to slowly replenish the pool. In
		246	addition to that, when the stacks used by a handler grows larger than 32kb
		247	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		248
		249	=cut
		250
		251	our $POOL_SIZE = 8;
		252	our $POOL_RSS = 32 * 1024;
		253	our @async_pool;
		254
		255	sub pool_handler {
		256	while () {
		257	eval {
		258	&{&_pool_handler} while 1;
		259	};
		260
		261	warn $@ if $@;
		262	}
		263	}
		264
		265	=back
		266
		267	=head1 STATIC METHODS
		268
		269	Static methods are actually functions that implicitly operate on the
		270	current coroutine.
		271
		272	=over 4
175		273
176	=item schedule	274	=item schedule
177		275
178	Calls the scheduler. Please note that the current process will not be put	276	Calls the scheduler. The scheduler will find the next coroutine that is
		277	to be run from the ready queue and switches to it. The next coroutine
		278	to be run is simply the one with the highest priority that is longest
		279	in its ready queue. If there is no coroutine ready, it will clal the
		280	C<$Coro::idle> hook.
		281
		282	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	283	queue, so calling this function usually means you will never be called
180	never be called again.	284	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		285	thus waking you up.
181		286
182	=cut	287	This makes C<schedule> I<the> generic method to use to block the current
		288	coroutine and wait for events: first you remember the current coroutine in
		289	a variable, then arrange for some callback of yours to call C<< ->ready
		290	>> on that once some event happens, and last you call C<schedule> to put
		291	yourself to sleep. Note that a lot of things can wake your coroutine up,
		292	so you need to check whether the event indeed happened, e.g. by storing the
		293	status in a variable.
		294
		295	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
183		296
184	=item cede	297	=item cede
185		298
186	"Cede" to other processes. This function puts the current process into the	299	"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	300	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.	301	up the current "timeslice" to other coroutines of the same or higher
		302	priority. Once your coroutine gets its turn again it will automatically be
		303	resumed.
189		304
190	=cut	305	This function is often called C<yield> in other languages.
		306
		307	=item Coro::cede_notself
		308
		309	Works like cede, but is not exported by default and will cede to I<any>
		310	coroutine, regardless of priority. This is useful sometimes to ensure
		311	progress is made.
191		312
192	=item terminate [arg...]	313	=item terminate [arg...]
193		314
194	Terminates the current process with the given status values (see L<cancel>).	315	Terminates the current coroutine with the given status values (see L<cancel>).
195		316
196	=cut	317	=item killall
197		318
198	sub terminate {	319	Kills/terminates/cancels all coroutines except the currently running
199	$current->cancel (@_);	320	one. This is useful after a fork, either in the child or the parent, as
		321	usually only one of them should inherit the running coroutines.
		322
		323	Note that while this will try to free some of the main programs resources,
		324	you cannot free all of them, so if a coroutine that is not the main
		325	program calls this function, there will be some one-time resource leak.
		326
		327	=cut
		328
		329	sub killall {
		330	for (Coro::State::list) {
		331	$_->cancel
		332	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		333	}
200	}	334	}
201		335
202	=back	336	=back
203		337
204	# dynamic methods	338	=head1 COROUTINE OBJECT METHODS
205		339
206	=head2 PROCESS METHODS
207
208	These are the methods you can call on process objects.	340	These are the methods you can call on coroutine objects (or to create
		341	them).
209		342
210	=over 4	343	=over 4
211		344
212	=item new Coro \&sub [, @args...]	345	=item new Coro \&sub [, @args...]
213		346
214	Create a new process and return it. When the sub returns the process	347	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	348	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	349	called. To make the coroutine run you must first put it into the ready
217	by calling the ready method.	350	queue by calling the ready method.
218		351
219	=cut	352	See C<async> and C<Coro::State::new> for additional info about the
		353	coroutine environment.
220		354
221	sub _newcoro {	355	=cut
		356
		357	sub _terminate {
222	terminate &{+shift};	358	terminate &{+shift};
223	}	359	}
224		360
225	sub new {	361	=item $success = $coroutine->ready
226	my $class = shift;
227	bless {
228	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229	}, $class;
230	}
231		362
232	=item $process->ready	363	Put the given coroutine into the end of its ready queue (there is one
		364	queue for each priority) and return true. If the coroutine is already in
		365	the ready queue, do nothing and return false.
233		366
234	Put the given process into the ready queue.	367	This ensures that the scheduler will resume this coroutine automatically
		368	once all the coroutines of higher priority and all coroutines of the same
		369	priority that were put into the ready queue earlier have been resumed.
235		370
236	=cut	371	=item $is_ready = $coroutine->is_ready
237		372
		373	Return whether the coroutine is currently the ready queue or not,
		374
238	=item $process->cancel (arg...)	375	=item $coroutine->cancel (arg...)
239		376
240	Temrinates the given process and makes it return the given arguments as	377	Terminates the given coroutine and makes it return the given arguments as
241	status (default: the empty list).	378	status (default: the empty list). Never returns if the coroutine is the
		379	current coroutine.
242		380
243	=cut	381	=cut
244		382
245	sub cancel {	383	sub cancel {
246	my $self = shift;	384	my $self = shift;
		385
		386	if ($current == $self) {
		387	terminate @_;
		388	} else {
247	$self->{status} = [@_];	389	$self->{_status} = [@_];
248	push @destroy, $self;	390	$self->_cancel;
249	$manager->ready;	391	}
250	&schedule if $current == $self;
251	}	392	}
252		393
		394	=item $coroutine->schedule_to
		395
		396	Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
		397	of continuing with the next coro from the ready queue, always switch to
		398	the given coroutine object (regardless of priority etc.). The readyness
		399	state of that coroutine isn't changed.
		400
		401	This is an advanced method for special cases - I'd love to hear about any
		402	uses for this one.
		403
		404	=item $coroutine->cede_to
		405
		406	Like C<schedule_to>, but puts the current coroutine into the ready
		407	queue. This has the effect of temporarily switching to the given
		408	coroutine, and continuing some time later.
		409
		410	This is an advanced method for special cases - I'd love to hear about any
		411	uses for this one.
		412
		413	=item $coroutine->throw ([$scalar])
		414
		415	If C<$throw> is specified and defined, it will be thrown as an exception
		416	inside the coroutine at the next convenient point in time. Otherwise
		417	clears the exception object.
		418
		419	Coro will check for the exception each time a schedule-like-function
		420	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		421	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		422	detect this case and return early in case an exception is pending.
		423
		424	The exception object will be thrown "as is" with the specified scalar in
		425	C<$@>, i.e. if it is a string, no line number or newline will be appended
		426	(unlike with C<die>).
		427
		428	This can be used as a softer means than C<cancel> to ask a coroutine to
		429	end itself, although there is no guarantee that the exception will lead to
		430	termination, and if the exception isn't caught it might well end the whole
		431	program.
		432
		433	You might also think of C<throw> as being the moral equivalent of
		434	C<kill>ing a coroutine with a signal (in this case, a scalar).
		435
253	=item $process->join	436	=item $coroutine->join
254		437
255	Wait until the coroutine terminates and return any values given to the	438	Wait until the coroutine terminates and return any values given to the
256	C<terminate> or C<cancel> functions. C<join> can be called multiple times	439	C<terminate> or C<cancel> functions. C<join> can be called concurrently
257	from multiple processes.	440	from multiple coroutines, and all will be resumed and given the status
		441	return once the C<$coroutine> terminates.
258		442
259	=cut	443	=cut
260		444
261	sub join {	445	sub join {
262	my $self = shift;	446	my $self = shift;
		447
263	unless ($self->{status}) {	448	unless ($self->{_status}) {
264	push @{$self->{join}}, $current;	449	my $current = $current;
265	&schedule;	450
		451	push @{$self->{_on_destroy}}, sub {
		452	$current->ready;
		453	undef $current;
		454	};
		455
		456	&schedule while $current;
266	}	457	}
		458
267	wantarray ? @{$self->{status}} : $self->{status}[0];	459	wantarray ? @{$self->{_status}} : $self->{_status}[0];
268	}	460	}
269		461
		462	=item $coroutine->on_destroy (\&cb)
		463
		464	Registers a callback that is called when this coroutine gets destroyed,
		465	but before it is joined. The callback gets passed the terminate arguments,
		466	if any, and I<must not> die, under any circumstances.
		467
		468	=cut
		469
		470	sub on_destroy {
		471	my ($self, $cb) = @_;
		472
		473	push @{ $self->{_on_destroy} }, $cb;
		474	}
		475
270	=item $oldprio = $process->prio($newprio)	476	=item $oldprio = $coroutine->prio ($newprio)
271		477
272	Sets (or gets, if the argument is missing) the priority of the	478	Sets (or gets, if the argument is missing) the priority of the
273	process. Higher priority processes get run before lower priority	479	coroutine. Higher priority coroutines get run before lower priority
274	processes. Priorities are small signed integers (currently -4 .. +3),	480	coroutines. Priorities are small signed integers (currently -4 .. +3),
275	that you can refer to using PRIO_xxx constants (use the import tag :prio	481	that you can refer to using PRIO_xxx constants (use the import tag :prio
276	to get then):	482	to get then):
277		483
278	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	484	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
279	3 > 1 > 0 > -1 > -3 > -4	485	3 > 1 > 0 > -1 > -3 > -4
282	current->prio(PRIO_HIGH);	488	current->prio(PRIO_HIGH);
283		489
284	The idle coroutine ($Coro::idle) always has a lower priority than any	490	The idle coroutine ($Coro::idle) always has a lower priority than any
285	existing coroutine.	491	existing coroutine.
286		492
287	Changing the priority of the current process will take effect immediately,	493	Changing the priority of the current coroutine will take effect immediately,
288	but changing the priority of processes in the ready queue (but not	494	but changing the priority of coroutines in the ready queue (but not
289	running) will only take effect after the next schedule (of that	495	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.	496	coroutine). This is a bug that will be fixed in some future version.
291		497
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)	498	=item $newprio = $coroutine->nice ($change)
301		499
302	Similar to C<prio>, but subtract the given value from the priority (i.e.	500	Similar to C<prio>, but subtract the given value from the priority (i.e.
303	higher values mean lower priority, just as in unix).	501	higher values mean lower priority, just as in unix).
304		502
305	=cut
306
307	sub nice {
308	$_[0]{prio} -= $_[1];
309	}
310
311	=item $olddesc = $process->desc($newdesc)	503	=item $olddesc = $coroutine->desc ($newdesc)
312		504
313	Sets (or gets in case the argument is missing) the description for this	505	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.	506	coroutine. This is just a free-form string you can associate with a
		507	coroutine.
		508
		509	This method simply sets the C<< $coroutine->{desc} >> member to the given
		510	string. You can modify this member directly if you wish.
315		511
316	=cut	512	=cut
317		513
318	sub desc {	514	sub desc {
319	my $old = $_[0]{desc};	515	my $old = $_[0]{desc};
320	$_[0]{desc} = $_[1] if @_ > 1;	516	$_[0]{desc} = $_[1] if @_ > 1;
321	$old;	517	$old;
322	}	518	}
323		519
		520	sub transfer {
		521	require Carp;
		522	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		523	}
		524
324	=back	525	=back
325		526
		527	=head1 GLOBAL FUNCTIONS
		528
		529	=over 4
		530
		531	=item Coro::nready
		532
		533	Returns the number of coroutines that are currently in the ready state,
		534	i.e. that can be switched to by calling C<schedule> directory or
		535	indirectly. The value C<0> means that the only runnable coroutine is the
		536	currently running one, so C<cede> would have no effect, and C<schedule>
		537	would cause a deadlock unless there is an idle handler that wakes up some
		538	coroutines.
		539
		540	=item my $guard = Coro::guard { ... }
		541
		542	This creates and returns a guard object. Nothing happens until the object
		543	gets destroyed, in which case the codeblock given as argument will be
		544	executed. This is useful to free locks or other resources in case of a
		545	runtime error or when the coroutine gets canceled, as in both cases the
		546	guard block will be executed. The guard object supports only one method,
		547	C<< ->cancel >>, which will keep the codeblock from being executed.
		548
		549	Example: set some flag and clear it again when the coroutine gets canceled
		550	or the function returns:
		551
		552	sub do_something {
		553	my $guard = Coro::guard { $busy = 0 };
		554	$busy = 1;
		555
		556	# do something that requires $busy to be true
		557	}
		558
		559	=cut
		560
		561	sub guard(&) {
		562	bless \(my $cb = $_[0]), "Coro::guard"
		563	}
		564
		565	sub Coro::guard::cancel {
		566	${$_[0]} = sub { };
		567	}
		568
		569	sub Coro::guard::DESTROY {
		570	${$_[0]}->();
		571	}
		572
		573
		574	=item unblock_sub { ... }
		575
		576	This utility function takes a BLOCK or code reference and "unblocks" it,
		577	returning a new coderef. Unblocking means that calling the new coderef
		578	will return immediately without blocking, returning nothing, while the
		579	original code ref will be called (with parameters) from within another
		580	coroutine.
		581
		582	The reason this function exists is that many event libraries (such as the
		583	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		584	of reentrancy). This means you must not block within event callbacks,
		585	otherwise you might suffer from crashes or worse. The only event library
		586	currently known that is safe to use without C<unblock_sub> is L<EV>.
		587
		588	This function allows your callbacks to block by executing them in another
		589	coroutine where it is safe to block. One example where blocking is handy
		590	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		591	disk, for example.
		592
		593	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		594	creating event callbacks that want to block.
		595
		596	If your handler does not plan to block (e.g. simply sends a message to
		597	another coroutine, or puts some other coroutine into the ready queue),
		598	there is no reason to use C<unblock_sub>.
		599
		600	Note that you also need to use C<unblock_sub> for any other callbacks that
		601	are indirectly executed by any C-based event loop. For example, when you
		602	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		603	provides callbacks that are the result of some event callback, then you
		604	must not block either, or use C<unblock_sub>.
		605
		606	=cut
		607
		608	our @unblock_queue;
		609
		610	# we create a special coro because we want to cede,
		611	# to reduce pressure on the coro pool (because most callbacks
		612	# return immediately and can be reused) and because we cannot cede
		613	# inside an event callback.
		614	our $unblock_scheduler = new Coro sub {
		615	while () {
		616	while (my $cb = pop @unblock_queue) {
		617	&async_pool (@$cb);
		618
		619	# for short-lived callbacks, this reduces pressure on the coro pool
		620	# as the chance is very high that the async_poll coro will be back
		621	# in the idle state when cede returns
		622	cede;
		623	}
		624	schedule; # sleep well
		625	}
		626	};
		627	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
		628
		629	sub unblock_sub(&) {
		630	my $cb = shift;
		631
		632	sub {
		633	unshift @unblock_queue, [$cb, @_];
		634	$unblock_scheduler->ready;
		635	}
		636	}
		637
		638	=item $cb = Coro::rouse_cb
		639
		640	Create and return a "rouse callback". That's a code reference that,
		641	when called, will remember a copy of its arguments and notify the owner
		642	coroutine of the callback.
		643
		644	See the next function.
		645
		646	=item @args = Coro::rouse_wait [$cb]
		647
		648	Wait for the specified rouse callback (or the last one that was created in
		649	this coroutine).
		650
		651	As soon as the callback is invoked (or when the callback was invoked
		652	before C<rouse_wait>), it will return the arguments originally passed to
		653	the rouse callback.
		654
		655	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		656
		657	=back
		658
326	=cut	659	=cut
327		660
328	1;	661	1;
329		662
		663	=head1 HOW TO WAIT FOR A CALLBACK
		664
		665	It is very common for a coroutine to wait for some callback to be
		666	called. This occurs naturally when you use coroutines in an otherwise
		667	event-based program, or when you use event-based libraries.
		668
		669	These typically register a callback for some event, and call that callback
		670	when the event occured. In a coroutine, however, you typically want to
		671	just wait for the event, simplyifying things.
		672
		673	For example C<< AnyEvent->child >> registers a callback to be called when
		674	a specific child has exited:
		675
		676	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		677
		678	But from withina coroutine, you often just want to write this:
		679
		680	my $status = wait_for_child $pid;
		681
		682	Coro offers two functions specifically designed to make this easy,
		683	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		684
		685	The first function, C<rouse_cb>, generates and returns a callback that,
		686	when invoked, will save it's arguments and notify the coroutine that
		687	created the callback.
		688
		689	The second function, C<rouse_wait>, waits for the callback to be called
		690	(by calling C<schedule> to go to sleep) and returns the arguments
		691	originally passed to the callback.
		692
		693	Using these functions, it becomes easy to write the C<wait_for_child>
		694	function mentioned above:
		695
		696	sub wait_for_child($) {
		697	my ($pid) = @_;
		698
		699	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		700
		701	my ($rpid, $rstatus) = Coro::rouse_wait;
		702	$rstatus
		703	}
		704
		705	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		706	you can roll your own, using C<schedule>:
		707
		708	sub wait_for_child($) {
		709	my ($pid) = @_;
		710
		711	# store the current coroutine in $current,
		712	# and provide result variables for the closure passed to ->child
		713	my $current = $Coro::current;
		714	my ($done, $rstatus);
		715
		716	# pass a closure to ->child
		717	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		718	$rstatus = $_[1]; # remember rstatus
		719	$done = 1; # mark $rstatus as valud
		720	});
		721
		722	# wait until the closure has been called
		723	schedule while !$done;
		724
		725	$rstatus
		726	}
		727
		728
330	=head1 BUGS/LIMITATIONS	729	=head1 BUGS/LIMITATIONS
331		730
332	- you must make very sure that no coro is still active on global	731	=over 4
333	destruction. very bad things might happen otherwise (usually segfaults).
334		732
		733	=item fork with pthread backend
		734
		735	When Coro is compiled using the pthread backend (which isn't recommended
		736	but required on many BSDs as their libcs are completely broken), then
		737	coroutines will not survive a fork. There is no known workaround except to
		738	fix your libc and use a saner backend.
		739
		740	=item perl process emulation ("threads")
		741
335	- this module is not thread-safe. You should only ever use this module	742	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	743	module from the first thread (this requirement might be removed in the
337	to allow per-thread schedulers, but Coro::State does not yet allow	744	future to allow per-thread schedulers, but Coro::State does not yet allow
338	this).	745	this). I recommend disabling thread support and using processes, as having
		746	the windows process emulation enabled under unix roughly halves perl
		747	performance, even when not used.
		748
		749	=item coroutine switching not signal safe
		750
		751	You must not switch to another coroutine from within a signal handler
		752	(only relevant with %SIG - most event libraries provide safe signals).
		753
		754	That means you I<MUST NOT> call any function that might "block" the
		755	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		756	anything that calls those. Everything else, including calling C<ready>,
		757	works.
		758
		759	=back
		760
339		761
340	=head1 SEE ALSO	762	=head1 SEE ALSO
341		763
342	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	764	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>,	765
344	L<Coro::Handle>, L<Coro::RWLock>, L<Coro::Socket>.	766	Debugging: L<Coro::Debug>.
		767
		768	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		769
		770	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		771	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		772
		773	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		774
		775	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		776	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		777	L<Coro::Select>.
		778
		779	XS API: L<Coro::MakeMaker>.
		780
		781	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
345		782
346	=head1 AUTHOR	783	=head1 AUTHOR
347		784
348	Marc Lehmann <schmorp@schmorp.de>	785	Marc Lehmann <schmorp@schmorp.de>
349	http://home.schmorp.de/	786	http://home.schmorp.de/

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Comparing Coro/Coro.pm (file contents):
Revision 1.66 by root, Thu Mar 3 17:20:31 2005 UTC vs.
Revision 1.239 by root, Mon Nov 24 07:55:28 2008 UTC