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

Comparing Coro/Coro.pm (file contents):
Revision 1.31 by root, Sat Aug 11 23:10:56 2001 UTC vs.
Revision 1.222 by root, Tue Nov 18 08:59:46 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
26	This module is still experimental, see the BUGS section below.	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.
27		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
28	In this module, coroutines are defined as "callchain + lexical variables	52	In this module, coroutines are defined as "callchain + lexical variables +
29	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own	53	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30	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
31	important global variables.	55	variables (see L<Coro::State> for more configuration).
32		56
33	=cut	57	=cut
34		58
35	package Coro;	59	package Coro;
36		60
		61	use strict qw(vars subs);
		62	no warnings "uninitialized";
		63
37	use Coro::State;	64	use Coro::State;
38		65
39	use base Exporter;	66	use base qw(Coro::State Exporter);
40		67
41	$VERSION = 0.45;	68	our $idle; # idle handler
		69	our $main; # main coroutine
		70	our $current; # current coroutine
42		71
		72	our $VERSION = 5.0;
		73
43	@EXPORT = qw(async cede schedule terminate current);	74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44	%EXPORT_TAGS = (	75	our %EXPORT_TAGS = (
45	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46	);	77	);
47	@EXPORT_OK = @{$EXPORT_TAGS{prio}};	78	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
48		79
49	{	80	=over 4
50	my @async;
51	my $init;
52		81
53	# this way of handling attributes simply is NOT scalable ;()
54	sub import {
55	Coro->export_to_level(1, @_);
56	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
57	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
58	my ($package, $ref) = (shift, shift);
59	my @attrs;
60	for (@_) {
61	if ($_ eq "Coro") {
62	push @async, $ref;
63	unless ($init++) {
64	eval q{
65	sub INIT {
66	&async(pop @async) while @async;
67	}
68	};
69	}
70	} else {
71	push @attrs, $_;
72	}
73	}
74	return $old ? $old->($package, $ref, @attrs) : @attrs;
75	};
76	}
77
78	}
79
80	=item $main	82	=item $Coro::main
81		83
82	This coroutine represents the main program.	84	This variable stores the coroutine object that represents the main
		85	program. While you cna C<ready> it and do most other things you can do to
		86	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		87	whether you are running in the main program or not.
83		88
84	=cut	89	=cut
85		90
86	our $main = new Coro;	91	# $main is now being initialised by Coro::State
87		92
88	=item $current (or as function: current)	93	=item $Coro::current
89		94
90	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	95	The coroutine object representing the current coroutine (the last
		96	coroutine that the Coro scheduler switched to). The initial value is
		97	C<$Coro::main> (of course).
91		98
92	=cut	99	This variable is B<strictly> I<read-only>. You can take copies of the
		100	value stored in it and use it as any other coroutine object, but you must
		101	not otherwise modify the variable itself.
93		102
94	# maybe some other module used Coro::Specific before...	103	=cut
95	if ($current) {
96	$main->{specific} = $current->{specific};
97	}
98		104
99	our $current = $main;
100
101	sub current() { $current }	105	sub current() { $current } # [DEPRECATED]
102		106
103	=item $idle	107	=item $Coro::idle
104		108
105	The coroutine to switch to when no other coroutine is running. The default	109	This variable is mainly useful to integrate Coro into event loops. It is
106	implementation prints "FATAL: deadlock detected" and exits.	110	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
		111	pretty low-level functionality.
107		112
108	=cut	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.
109		117
110	# should be done using priorities :(	118	This hook is overwritten by modules such as C<Coro::Timer> and
111	our $idle = new Coro sub {	119	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
112	print STDERR "FATAL: deadlock detected\n";	120	coroutine so the scheduler can run it.
113	exit(51);	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
		130	Please note that if your callback recursively invokes perl (e.g. for event
		131	handlers), then it must be prepared to be called recursively itself.
		132
		133	=cut
		134
		135	$idle = sub {
		136	require Carp;
		137	Carp::croak ("FATAL: deadlock detected");
114	};	138	};
		139
		140	sub _cancel {
		141	my ($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	}
115		151
116	# this coroutine is necessary because a coroutine	152	# this coroutine is necessary because a coroutine
117	# cannot destroy itself.	153	# cannot destroy itself.
118	my @destroy;	154	my @destroy;
		155	my $manager;
		156
119	my $manager = new Coro sub {	157	$manager = new Coro sub {
120	while() {	158	while () {
121	delete ((pop @destroy)->{_coro_state}) while @destroy;	159	(shift @destroy)->_cancel
		160	while @destroy;
		161
122	&schedule;	162	&schedule;
123	}	163	}
124	};	164	};
		165	$manager->{desc} = "[coro manager]";
		166	$manager->prio (PRIO_MAX);
125		167
126	# static methods. not really.	168	=back
127		169
128	=head2 STATIC METHODS	170	=head2 SIMPLE COROUTINE CREATION
129
130	Static methods are actually functions that operate on the current process only.
131		171
132	=over 4	172	=over 4
133		173
134	=item async { ... } [@args...]	174	=item async { ... } [@args...]
135		175
136	Create a new asynchronous process and return it's process object	176	Create a new coroutine and return it's coroutine object (usually
137	(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
138	terminated.	182	terminated.
139		183
		184	The remaining arguments are passed as arguments to the closure.
		185
		186	See the C<Coro::State::new> constructor for info about the coroutine
		187	environment in which coroutines are executed.
		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
140	# create a new coroutine that just prints its arguments	196	Example: Create a new coroutine that just prints its arguments.
		197
141	async {	198	async {
142	print "@_\n";	199	print "@_\n";
143	} 1,2,3,4;	200	} 1,2,3,4;
144		201
145	The coderef you submit MUST NOT be a closure that refers to variables
146	in an outer scope. This does NOT work. Pass arguments into it instead.
147
148	=cut	202	=cut
149		203
150	sub async(&@) {	204	sub async(&@) {
151	my $pid = new Coro @_;	205	my $coro = new Coro @_;
152	$manager->ready; # this ensures that the stack is cloned from the manager
153	$pid->ready;	206	$coro->ready;
154	$pid;	207	$coro
155	}	208	}
		209
		210	=item async_pool { ... } [@args...]
		211
		212	Similar to C<async>, but uses a coroutine pool, so you should not call
		213	terminate or join on it (although you are allowed to), and you get a
		214	coroutine that might have executed other code already (which can be good
		215	or bad :).
		216
		217	On the plus side, this function is faster than creating (and destroying)
		218	a completly new coroutine, so if you need a lot of generic coroutines in
		219	quick successsion, use C<async_pool>, not C<async>.
		220
		221	The code block is executed in an C<eval> context and a warning will be
		222	issued in case of an exception instead of terminating the program, as
		223	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		224	will not work in the expected way, unless you call terminate or cancel,
		225	which somehow defeats the purpose of pooling (but is fine in the
		226	exceptional case).
		227
		228	The priority will be reset to C<0> after each run, tracing will be
		229	disabled, the description will be reset and the default output filehandle
		230	gets restored, so you can change all these. Otherwise the coroutine will
		231	be re-used "as-is": most notably if you change other per-coroutine global
		232	stuff such as C<$/> 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	$coro
		279	}
		280
		281	=back
		282
		283	=head2 STATIC METHODS
		284
		285	Static methods are actually functions that operate on the current coroutine.
		286
		287	=over 4
156		288
157	=item schedule	289	=item schedule
158		290
159	Calls the scheduler. Please note that the current process will not be put	291	Calls the scheduler. The scheduler will find the next coroutine that is
		292	to be run from the ready queue and switches to it. The next coroutine
		293	to be run is simply the one with the highest priority that is longest
		294	in its ready queue. If there is no coroutine ready, it will clal the
		295	C<$Coro::idle> hook.
		296
		297	Please note that the current coroutine will I<not> be put into the ready
160	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
161	never be called again.	299	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		300	thus waking you up.
162		301
163	=cut	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.
		309
		310	The canonical way to wait on external events is this:
		311
		312	{
		313	# remember current coroutine
		314	my $current = $Coro::current;
		315
		316	# register a hypothetical event handler
		317	on_event_invoke sub {
		318	# wake up sleeping coroutine
		319	$current->ready;
		320	undef $current;
		321	};
		322
		323	# call schedule until event occurred.
		324	# in case we are woken up for other reasons
		325	# (current still defined), loop.
		326	Coro::schedule while $current;
		327	}
164		328
165	=item cede	329	=item cede
166		330
167	"Cede" to other processes. This function puts the current process into the	331	"Cede" to other coroutines. This function puts the current coroutine into
168	ready queue and calls C<schedule>, which has the effect of giving up the	332	the ready queue and calls C<schedule>, which has the effect of giving
169	current "timeslice" to other coroutines of the same or higher priority.	333	up the current "timeslice" to other coroutines of the same or higher
		334	priority. Once your coroutine gets its turn again it will automatically be
		335	resumed.
170		336
171	=cut	337	This function is often called C<yield> in other languages.
172		338
		339	=item Coro::cede_notself
		340
		341	Works like cede, but is not exported by default and will cede to I<any>
		342	coroutine, regardless of priority. This is useful sometimes to ensure
		343	progress is made.
		344
173	=item terminate	345	=item terminate [arg...]
174		346
175	Terminates the current process.	347	Terminates the current coroutine with the given status values (see L<cancel>).
176		348
177	Future versions of this function will allow result arguments.	349	=item killall
		350
		351	Kills/terminates/cancels all coroutines except the currently running
		352	one. This is useful after a fork, either in the child or the parent, as
		353	usually only one of them should inherit the running coroutines.
		354
		355	Note that while this will try to free some of the main programs resources,
		356	you cannot free all of them, so if a coroutine that is not the main
		357	program calls this function, there will be some one-time resource leak.
178		358
179	=cut	359	=cut
180		360
181	sub terminate {	361	sub terminate {
182	$current->cancel;	362	$current->cancel (@_);
183	&schedule;	363	}
184	die; # NORETURN	364
		365	sub killall {
		366	for (Coro::State::list) {
		367	$_->cancel
		368	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		369	}
185	}	370	}
186		371
187	=back	372	=back
188		373
189	# dynamic methods
190
191	=head2 PROCESS METHODS	374	=head2 COROUTINE METHODS
192		375
193	These are the methods you can call on process objects.	376	These are the methods you can call on coroutine objects (or to create
		377	them).
194		378
195	=over 4	379	=over 4
196		380
197	=item new Coro \&sub [, @args...]	381	=item new Coro \&sub [, @args...]
198		382
199	Create a new process and return it. When the sub returns the process	383	Create a new coroutine and return it. When the sub returns, the coroutine
200	automatically terminates. To start the process you must first put it into	384	automatically terminates as if C<terminate> with the returned values were
		385	called. To make the coroutine run you must first put it into the ready
201	the ready queue by calling the ready method.	386	queue by calling the ready method.
202		387
203	The coderef you submit MUST NOT be a closure that refers to variables	388	See C<async> and C<Coro::State::new> for additional info about the
204	in an outer scope. This does NOT work. Pass arguments into it instead.	389	coroutine environment.
205		390
206	=cut	391	=cut
207		392
208	sub _newcoro {	393	sub _run_coro {
209	terminate &{+shift};	394	terminate &{+shift};
210	}	395	}
211		396
212	sub new {	397	sub new {
213	my $class = shift;	398	my $class = shift;
214	bless {
215	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
216	}, $class;
217	}
218		399
219	=item $process->ready	400	$class->SUPER::new (\&_run_coro, @_)
		401	}
220		402
221	Put the current process into the ready queue.	403	=item $success = $coroutine->ready
222		404
223	=cut	405	Put the given coroutine into the end of its ready queue (there is one
		406	queue for each priority) and return true. If the coroutine is already in
		407	the ready queue, do nothing and return false.
224		408
225	=item $process->cancel	409	This ensures that the scheduler will resume this coroutine automatically
		410	once all the coroutines of higher priority and all coroutines of the same
		411	priority that were put into the ready queue earlier have been resumed.
226		412
227	Like C<terminate>, but terminates the specified process instead.	413	=item $is_ready = $coroutine->is_ready
		414
		415	Return whether the coroutine is currently the ready queue or not,
		416
		417	=item $coroutine->cancel (arg...)
		418
		419	Terminates the given coroutine and makes it return the given arguments as
		420	status (default: the empty list). Never returns if the coroutine is the
		421	current coroutine.
228		422
229	=cut	423	=cut
230		424
231	sub cancel {	425	sub cancel {
		426	my $self = shift;
		427	$self->{_status} = [@_];
		428
		429	if ($current == $self) {
232	push @destroy, $_[0];	430	push @destroy, $self;
233	$manager->ready;	431	$manager->ready;
		432	&schedule while 1;
		433	} else {
		434	$self->_cancel;
		435	}
234	}	436	}
235		437
		438	=item $coroutine->throw ([$scalar])
		439
		440	If C<$throw> is specified and defined, it will be thrown as an exception
		441	inside the coroutine at the next convenient point in time. Otherwise
		442	clears the exception object.
		443
		444	Coro will check for the exception each time a schedule-like-function
		445	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		446	>>, C<< Coro::Handle->readable >> and so on. Note that this means that
		447	when a coroutine is acquiring a lock, it might only throw after it has
		448	sucessfully acquired it.
		449
		450	The exception object will be thrown "as is" with the specified scalar in
		451	C<$@>, i.e. if it is a string, no line number or newline will be appended
		452	(unlike with C<die>).
		453
		454	This can be used as a softer means than C<cancel> to ask a coroutine to
		455	end itself, although there is no guarantee that the exception will lead to
		456	termination, and if the exception isn't caught it might well end the whole
		457	program.
		458
		459	You might also think of C<throw> as being the moral equivalent of
		460	C<kill>ing a coroutine with a signal (in this case, a scalar).
		461
		462	=item $coroutine->join
		463
		464	Wait until the coroutine terminates and return any values given to the
		465	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		466	from multiple coroutines, and all will be resumed and given the status
		467	return once the C<$coroutine> terminates.
		468
		469	=cut
		470
		471	sub join {
		472	my $self = shift;
		473
		474	unless ($self->{_status}) {
		475	my $current = $current;
		476
		477	push @{$self->{_on_destroy}}, sub {
		478	$current->ready;
		479	undef $current;
		480	};
		481
		482	&schedule while $current;
		483	}
		484
		485	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		486	}
		487
		488	=item $coroutine->on_destroy (\&cb)
		489
		490	Registers a callback that is called when this coroutine gets destroyed,
		491	but before it is joined. The callback gets passed the terminate arguments,
		492	if any, and I<must not> die, under any circumstances.
		493
		494	=cut
		495
		496	sub on_destroy {
		497	my ($self, $cb) = @_;
		498
		499	push @{ $self->{_on_destroy} }, $cb;
		500	}
		501
236	=item $oldprio = $process->prio($newprio)	502	=item $oldprio = $coroutine->prio ($newprio)
237		503
238	Sets the priority of the process. Higher priority processes get run before	504	Sets (or gets, if the argument is missing) the priority of the
239	lower priority processes. Priorities are smalled signed integer (currently	505	coroutine. Higher priority coroutines get run before lower priority
		506	coroutines. Priorities are small signed integers (currently -4 .. +3),
240	-4 .. +3), that you can refer to using PRIO_xxx constants (use the import	507	that you can refer to using PRIO_xxx constants (use the import tag :prio
241	tag :prio to get then):	508	to get then):
242		509
243	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	510	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
244	3 > 1 > 0 > -1 > -3 > -4	511	3 > 1 > 0 > -1 > -3 > -4
245		512
246	# set priority to HIGH	513	# set priority to HIGH
247	current->prio(PRIO_HIGH);	514	current->prio(PRIO_HIGH);
248		515
249	The idle coroutine ($Coro::idle) always has a lower priority than any	516	The idle coroutine ($Coro::idle) always has a lower priority than any
250	existing coroutine.	517	existing coroutine.
251		518
252	Changing the priority of the current process will take effect immediately,	519	Changing the priority of the current coroutine will take effect immediately,
253	but changing the priority of processes in the ready queue (but not	520	but changing the priority of coroutines in the ready queue (but not
254	running) will only take effect after the next schedule (of that	521	running) will only take effect after the next schedule (of that
255	process). This is a bug that will be fixed in some future version.	522	coroutine). This is a bug that will be fixed in some future version.
256		523
257	=cut
258
259	sub prio {
260	my $old = $_[0]{prio};
261	$_[0]{prio} = $_[1] if @_ > 1;
262	$old;
263	}
264
265	=item $newprio = $process->nice($change)	524	=item $newprio = $coroutine->nice ($change)
266		525
267	Similar to C<prio>, but subtract the given value from the priority (i.e.	526	Similar to C<prio>, but subtract the given value from the priority (i.e.
268	higher values mean lower priority, just as in unix).	527	higher values mean lower priority, just as in unix).
269		528
270	=cut	529	=item $olddesc = $coroutine->desc ($newdesc)
271		530
272	sub nice {	531	Sets (or gets in case the argument is missing) the description for this
273	$_[0]{prio} -= $_[1];	532	coroutine. This is just a free-form string you can associate with a
		533	coroutine.
		534
		535	This method simply sets the C<< $coroutine->{desc} >> member to the given
		536	string. You can modify this member directly if you wish.
		537
		538	=cut
		539
		540	sub desc {
		541	my $old = $_[0]{desc};
		542	$_[0]{desc} = $_[1] if @_ > 1;
		543	$old;
274	}	544	}
275		545
276	=back	546	=back
277		547
		548	=head2 GLOBAL FUNCTIONS
		549
		550	=over 4
		551
		552	=item Coro::nready
		553
		554	Returns the number of coroutines that are currently in the ready state,
		555	i.e. that can be switched to by calling C<schedule> directory or
		556	indirectly. The value C<0> means that the only runnable coroutine is the
		557	currently running one, so C<cede> would have no effect, and C<schedule>
		558	would cause a deadlock unless there is an idle handler that wakes up some
		559	coroutines.
		560
		561	=item my $guard = Coro::guard { ... }
		562
		563	This creates and returns a guard object. Nothing happens until the object
		564	gets destroyed, in which case the codeblock given as argument will be
		565	executed. This is useful to free locks or other resources in case of a
		566	runtime error or when the coroutine gets canceled, as in both cases the
		567	guard block will be executed. The guard object supports only one method,
		568	C<< ->cancel >>, which will keep the codeblock from being executed.
		569
		570	Example: set some flag and clear it again when the coroutine gets canceled
		571	or the function returns:
		572
		573	sub do_something {
		574	my $guard = Coro::guard { $busy = 0 };
		575	$busy = 1;
		576
		577	# do something that requires $busy to be true
		578	}
		579
		580	=cut
		581
		582	sub guard(&) {
		583	bless \(my $cb = $_[0]), "Coro::guard"
		584	}
		585
		586	sub Coro::guard::cancel {
		587	${$_[0]} = sub { };
		588	}
		589
		590	sub Coro::guard::DESTROY {
		591	${$_[0]}->();
		592	}
		593
		594
		595	=item unblock_sub { ... }
		596
		597	This utility function takes a BLOCK or code reference and "unblocks" it,
		598	returning a new coderef. Unblocking means that calling the new coderef
		599	will return immediately without blocking, returning nothing, while the
		600	original code ref will be called (with parameters) from within another
		601	coroutine.
		602
		603	The reason this function exists is that many event libraries (such as the
		604	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		605	of thread-safety). This means you must not block within event callbacks,
		606	otherwise you might suffer from crashes or worse. The only event library
		607	currently known that is safe to use without C<unblock_sub> is L<EV>.
		608
		609	This function allows your callbacks to block by executing them in another
		610	coroutine where it is safe to block. One example where blocking is handy
		611	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		612	disk, for example.
		613
		614	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		615	creating event callbacks that want to block.
		616
		617	If your handler does not plan to block (e.g. simply sends a message to
		618	another coroutine, or puts some other coroutine into the ready queue),
		619	there is no reason to use C<unblock_sub>.
		620
		621	Note that you also need to use C<unblock_sub> for any other callbacks that
		622	are indirectly executed by any C-based event loop. For example, when you
		623	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		624	provides callbacks that are the result of some event callback, then you
		625	must not block either, or use C<unblock_sub>.
		626
		627	=cut
		628
		629	our @unblock_queue;
		630
		631	# we create a special coro because we want to cede,
		632	# to reduce pressure on the coro pool (because most callbacks
		633	# return immediately and can be reused) and because we cannot cede
		634	# inside an event callback.
		635	our $unblock_scheduler = new Coro sub {
		636	while () {
		637	while (my $cb = pop @unblock_queue) {
		638	# this is an inlined copy of async_pool
		639	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		640
		641	$coro->{_invoke} = $cb;
		642	$coro->ready;
		643	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		644	}
		645	schedule; # sleep well
		646	}
		647	};
		648	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
		649
		650	sub unblock_sub(&) {
		651	my $cb = shift;
		652
		653	sub {
		654	unshift @unblock_queue, [$cb, @_];
		655	$unblock_scheduler->ready;
		656	}
		657	}
		658
		659	=back
		660
278	=cut	661	=cut
279		662
280	1;	663	1;
281		664
282	=head1 BUGS/LIMITATIONS	665	=head1 BUGS/LIMITATIONS
283		666
284	- could be faster, especially when the core would introduce special	667	=over 4
285	support for coroutines (like it does for threads).	668
286	- there is still a memleak on coroutine termination that I could not	669	=item fork with pthread backend
287	identify. Could be as small as a single SV.	670
288	- this module is not well-tested.	671	When Coro is compiled using the pthread backend (which isn't recommended
289	- if variables or arguments "disappear" (become undef) or become	672	but required on many BSDs as their libcs are completely broken), then
290	corrupted please contact the author so he cen iron out the	673	coroutines will not survive a fork. There is no known workaround except to
291	remaining bugs.	674	fix your libc and use a saner backend.
292	- this module is not thread-safe. You must only ever use this module from	675
		676	=item perl process emulation ("threads")
		677
		678	This module is not perl-pseudo-thread-safe. You should only ever use this
293	the same thread (this requirement might be loosened in the future to	679	module from the same thread (this requirement might be removed in the
294	allow per-thread schedulers, but Coro::State does not yet allow this).	680	future to allow per-thread schedulers, but Coro::State does not yet allow
		681	this). I recommend disabling thread support and using processes, as having
		682	the windows process emulation enabled under unix roughly halves perl
		683	performance, even when not used.
		684
		685	=item coroutine switching not signal safe
		686
		687	You must not switch to another coroutine from within a signal handler
		688	(only relevant with %SIG - most event libraries provide safe signals).
		689
		690	That means you I<MUST NOT> call any function that might "block" the
		691	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		692	anything that calls those. Everything else, including calling C<ready>,
		693	works.
		694
		695	=back
		696
295		697
296	=head1 SEE ALSO	698	=head1 SEE ALSO
297		699
298	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	700	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
299	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,	701
300	L<Coro::Handle>, L<Coro::Socket>.	702	Debugging: L<Coro::Debug>.
		703
		704	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		705
		706	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		707
		708	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		709
		710	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		711
		712	XS API: L<Coro::MakeMaker>.
		713
		714	Low level Configuration, Coroutine Environment: L<Coro::State>.
301		715
302	=head1 AUTHOR	716	=head1 AUTHOR
303		717
304	Marc Lehmann <pcg@goof.com>	718	Marc Lehmann <schmorp@schmorp.de>
305	http://www.goof.com/pcg/marc/	719	http://home.schmorp.de/
306		720
307	=cut	721	=cut
308		722

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Revision 1.222 by root, Tue Nov 18 08:59:46 2008 UTC