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

Comparing Coro/Coro.pm (file contents):
Revision 1.65 by root, Tue Feb 22 19:51:58 2005 UTC vs.
Revision 1.263 by root, Tue Jul 28 02:04:21 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 process 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 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 in
		35	the form of cooperative threads (also called coros, or simply "coro"
		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.
		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
26	In this module, coroutines are defined as "callchain + lexical variables	60	In this module, a thread is defined as "callchain + lexical variables +
27	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own	61	some package variables + C stack), that is, a thread has its own callchain,
28	callchain, it's own set of lexicals and it's own set of perl's most	62	its own set of lexicals and its own set of perls most important global
29	important global variables.	63	variables (see L<Coro::State> for more configuration and background info).
		64
		65	See also the C<SEE ALSO> section at the end of this document - the Coro
		66	module family is quite large.
30		67
31	=cut	68	=cut
32		69
33	package Coro;	70	package Coro;
34		71
35	BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") }	72	use strict qw(vars subs);
		73	no warnings "uninitialized";
		74
		75	use Guard ();
36		76
37	use Coro::State;	77	use Coro::State;
38		78
39	use vars qw($idle $main $current);	79	use base qw(Coro::State Exporter);
40		80
41	use base Exporter;	81	our $idle; # idle handler
		82	our $main; # main coro
		83	our $current; # current coro
42		84
43	$VERSION = 1.1;	85	our $VERSION = 5.162;
44		86
45	@EXPORT = qw(async cede schedule terminate current);	87	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46	%EXPORT_TAGS = (	88	our %EXPORT_TAGS = (
47	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	89	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48	);	90	);
49	@EXPORT_OK = @{$EXPORT_TAGS{prio}};	91	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
50		92
51	{	93	=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		94
82	=over 4	95	=over 4
83		96
84	=item $main	97	=item $Coro::main
85		98
86	This coroutine represents the main program.	99	This variable stores the Coro object that represents the main
		100	program. While you cna C<ready> it and do most other things you can do to
		101	coro, it is mainly useful to compare again C<$Coro::current>, to see
		102	whether you are running in the main program or not.
87		103
88	=cut	104	=cut
89		105
90	$main = new Coro;	106	# $main is now being initialised by Coro::State
91		107
92	=item $current (or as function: current)	108	=item $Coro::current
93		109
94	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	110	The Coro object representing the current coro (the last
		111	coro that the Coro scheduler switched to). The initial value is
		112	C<$Coro::main> (of course).
95		113
96	=cut	114	This variable is B<strictly> I<read-only>. You can take copies of the
		115	value stored in it and use it as any other Coro object, but you must
		116	not otherwise modify the variable itself.
97		117
98	# maybe some other module used Coro::Specific before...	118	=cut
99	if ($current) {
100	$main->{specific} = $current->{specific};
101	}
102		119
103	$current = $main;
104
105	sub current() { $current }	120	sub current() { $current } # [DEPRECATED]
106		121
107	=item $idle	122	=item $Coro::idle
108		123
109	The coroutine to switch to when no other coroutine is running. The default	124	This variable is mainly useful to integrate Coro into event loops. It is
110	implementation prints "FATAL: deadlock detected" and exits.	125	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		126	pretty low-level functionality.
111		127
112	=cut	128	This variable stores either a Coro object or a callback.
113		129
114	# should be done using priorities :(	130	If it is a callback, the it is called whenever the scheduler finds no
115	$idle = new Coro sub {	131	ready coros to run. The default implementation prints "FATAL:
116	print STDERR "FATAL: deadlock detected\n";	132	deadlock detected" and exits, because the program has no other way to
117	exit(51);	133	continue.
		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
		139	This hook is overwritten by modules such as C<Coro::EV> and
		140	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
		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.
		151
		152	Please note that if your callback recursively invokes perl (e.g. for event
		153	handlers), then it must be prepared to be called recursively itself.
		154
		155	=cut
		156
		157	$idle = sub {
		158	require Carp;
		159	Carp::croak ("FATAL: deadlock detected");
118	};	160	};
119		161
120	# this coroutine is necessary because a coroutine	162	# this coro is necessary because a coro
121	# cannot destroy itself.	163	# cannot destroy itself.
122	my @destroy;	164	our @destroy;
123	my $manager;	165	our $manager;
		166
124	$manager = new Coro sub {	167	$manager = new Coro sub {
125	while () {	168	while () {
126	# by overwriting the state object with the manager we destroy it	169	Coro::State::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) {	170	while @destroy;
132	my $coro = pop @destroy;
133	$coro->{status} \|\|= [];
134	$_->ready for @{delete $coro->{join} \|\| []};
135		171
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;	172	&schedule;
143	}	173	}
144	};	174	};
145		175	$manager->{desc} = "[coro manager]";
146	# static methods. not really.	176	$manager->prio (PRIO_MAX);
147		177
148	=back	178	=back
149		179
150	=head2 STATIC METHODS	180	=head1 SIMPLE CORO CREATION
151
152	Static methods are actually functions that operate on the current process only.
153		181
154	=over 4	182	=over 4
155		183
156	=item async { ... } [@args...]	184	=item async { ... } [@args...]
157		185
158	Create a new asynchronous process and return it's process object	186	Create a new coro and return its Coro object (usually
159	(usually unused). When the sub returns the new process 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
160	terminated.	192	terminated.
161		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
		199	Calling C<exit> in a coro will do the same as calling exit outside
		200	the coro. Likewise, when the coro dies, the program will exit,
		201	just as it would in the main program.
		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
162	# create a new coroutine that just prints its arguments	206	Example: Create a new coro that just prints its arguments.
		207
163	async {	208	async {
164	print "@_\n";	209	print "@_\n";
165	} 1,2,3,4;	210	} 1,2,3,4;
166		211
167	=cut	212	=cut
168		213
169	sub async(&@) {	214	sub async(&@) {
170	my $pid = new Coro @_;	215	my $coro = new Coro @_;
171	$manager->ready; # this ensures that the stack is cloned from the manager
172	$pid->ready;	216	$coro->ready;
173	$pid;	217	$coro
174	}	218	}
		219
		220	=item async_pool { ... } [@args...]
		221
		222	Similar to C<async>, but uses a coro pool, so you should not call
		223	terminate or join on it (although you are allowed to), and you get a
		224	coro that might have executed other code already (which can be good
		225	or bad :).
		226
		227	On the plus side, this function is about twice as fast as creating (and
		228	destroying) a completely new coro, so if you need a lot of generic
		229	coros in quick successsion, use C<async_pool>, not C<async>.
		230
		231	The code block is executed in an C<eval> context and a warning will be
		232	issued in case of an exception instead of terminating the program, as
		233	C<async> does. As the coro is being reused, stuff like C<on_destroy>
		234	will not work in the expected way, unless you call terminate or cancel,
		235	which somehow defeats the purpose of pooling (but is fine in the
		236	exceptional case).
		237
		238	The priority will be reset to C<0> after each run, tracing will be
		239	disabled, the description will be reset and the default output filehandle
		240	gets restored, so you can change all these. Otherwise the coro will
		241	be re-used "as-is": most notably if you change other per-coro global
		242	stuff such as C<$/> you I<must needs> revert that change, which is most
		243	simply done by using local as in: C<< local $/ >>.
		244
		245	The idle pool size is limited to C<8> idle coros (this can be
		246	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		247	coros as required.
		248
		249	If you are concerned about pooled coros growing a lot because a
		250	single C<async_pool> used a lot of stackspace you can e.g. C<async_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.
		254
		255	=cut
		256
		257	our $POOL_SIZE = 8;
		258	our $POOL_RSS = 32 * 1024;
		259	our @async_pool;
		260
		261	sub pool_handler {
		262	while () {
		263	eval {
		264	&{&_pool_handler} while 1;
		265	};
		266
		267	warn $@ if $@;
		268	}
		269	}
		270
		271	=back
		272
		273	=head1 STATIC METHODS
		274
		275	Static methods are actually functions that implicitly operate on the
		276	current coro.
		277
		278	=over 4
175		279
176	=item schedule	280	=item schedule
177		281
178	Calls the scheduler. Please note that the current process will not be put	282	Calls the scheduler. The scheduler will find the next coro that is
		283	to be run from the ready queue and switches to it. The next coro
		284	to be run is simply the one with the highest priority that is longest
		285	in its ready queue. If there is no coro ready, it will clal the
		286	C<$Coro::idle> hook.
		287
		288	Please note that the current coro will I<not> be put into the ready
179	into the ready queue, so calling this function usually means you will	289	queue, so calling this function usually means you will never be called
180	never be called again.	290	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		291	thus waking you up.
181		292
182	=cut	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.
183		302
184	=item cede	303	=item cede
185		304
186	"Cede" to other processes. This function puts the current process into the	305	"Cede" to other coros. This function puts the current coro into
187	ready queue and calls C<schedule>, which has the effect of giving up the	306	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.	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.
189		310
190	=cut	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.
191		318
192	=item terminate [arg...]	319	=item terminate [arg...]
193		320
194	Terminates the current process with the given status values (see L<cancel>).	321	Terminates the current coro with the given status values (see L<cancel>).
195		322
196	=cut	323	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
197		324
198	sub terminate {	325	These function install enter and leave winders in the current scope. The
199	$current->cancel (@_);	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 thread switching considerably for coros that use them
		344	(about 40% for a BLOCK with a single assignment, so thread switching is
		345	still reasonably fast if the handlers are 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.
		373	};
		374
		375	This can be used to localise about any resource (locale, uid, current
		376	working directory etc.) to a block, despite the existance of other
		377	coros.
		378
		379	Another interesting example implements time-sliced multitasking using
		380	interval timers (this could obviously be optimised, but does the job):
		381
		382	# "timeslice" the given block
		383	sub timeslice(&) {
		384	use Time::HiRes ();
		385
		386	Coro::on_enter {
		387	# on entering the thread, we set an VTALRM handler to cede
		388	$SIG{VTALRM} = sub { cede };
		389	# and then start the interval timer
		390	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		391	};
		392	Coro::on_leave {
		393	# on leaving the thread, we stop the interval timer again
		394	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		395	};
		396
		397	&{+shift};
		398	}
		399
		400	# use like this:
		401	timeslice {
		402	# The following is an endless loop that would normally
		403	# monopolise the process. Since it runs in a timesliced
		404	# environment, it will regularly cede to other threads.
		405	while () { }
		406	};
		407
		408
		409	=item killall
		410
		411	Kills/terminates/cancels all coros except the currently running one.
		412
		413	Note that while this will try to free some of the main interpreter
		414	resources if the calling coro isn't the main coro, but one
		415	cannot free all of them, so if a coro that is not the main coro
		416	calls this function, there will be some one-time resource leak.
		417
		418	=cut
		419
		420	sub killall {
		421	for (Coro::State::list) {
		422	$_->cancel
		423	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		424	}
200	}	425	}
201		426
202	=back	427	=back
203		428
204	# dynamic methods	429	=head1 CORO OBJECT METHODS
205		430
206	=head2 PROCESS METHODS
207
208	These are the methods you can call on process objects.	431	These are the methods you can call on coro objects (or to create
		432	them).
209		433
210	=over 4	434	=over 4
211		435
212	=item new Coro \&sub [, @args...]	436	=item new Coro \&sub [, @args...]
213		437
214	Create a new process and return it. When the sub returns the process	438	Create a new coro and return it. When the sub returns, the coro
215	automatically terminates as if C<terminate> with the returned values were	439	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	440	called. To make the coro run you must first put it into the ready
217	by calling the ready method.	441	queue by calling the ready method.
218		442
219	=cut	443	See C<async> and C<Coro::State::new> for additional info about the
		444	coro environment.
220		445
		446	=cut
		447
221	sub _newcoro {	448	sub _coro_run {
222	terminate &{+shift};	449	terminate &{+shift};
223	}	450	}
224		451
225	sub new {	452	=item $success = $coro->ready
226	my $class = shift;
227	bless {
228	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229	}, $class;
230	}
231		453
232	=item $process->ready	454	Put the given coro into the end of its ready queue (there is one
		455	queue for each priority) and return true. If the coro is already in
		456	the ready queue, do nothing and return false.
233		457
234	Put the given process into the ready queue.	458	This ensures that the scheduler will resume this coro automatically
		459	once all the coro of higher priority and all coro of the same
		460	priority that were put into the ready queue earlier have been resumed.
235		461
236	=cut	462	=item $coro->suspend
237		463
		464	Suspends the specified coro. A suspended coro works just like any other
		465	coro, except that the scheduler will not select a suspended coro for
		466	execution.
		467
		468	Suspending a coro can be useful when you want to keep the coro from
		469	running, but you don't want to destroy it, or when you want to temporarily
		470	freeze a coro (e.g. for debugging) to resume it later.
		471
		472	A scenario for the former would be to suspend all (other) coros after a
		473	fork and keep them alive, so their destructors aren't called, but new
		474	coros can be created.
		475
		476	=item $coro->resume
		477
		478	If the specified coro was suspended, it will be resumed. Note that when
		479	the coro was in the ready queue when it was suspended, it might have been
		480	unreadied by the scheduler, so an activation might have been lost.
		481
		482	To avoid this, it is best to put a suspended coro into the ready queue
		483	unconditionally, as every synchronisation mechanism must protect itself
		484	against spurious wakeups, and the one in the Coro family certainly do
		485	that.
		486
		487	=item $is_ready = $coro->is_ready
		488
		489	Returns true iff the Coro object is in the ready queue. Unless the Coro
		490	object gets destroyed, it will eventually be scheduled by the scheduler.
		491
		492	=item $is_running = $coro->is_running
		493
		494	Returns true iff the Coro object is currently running. Only one Coro object
		495	can ever be in the running state (but it currently is possible to have
		496	multiple running Coro::States).
		497
		498	=item $is_suspended = $coro->is_suspended
		499
		500	Returns true iff this Coro object has been suspended. Suspended Coros will
		501	not ever be scheduled.
		502
238	=item $process->cancel (arg...)	503	=item $coro->cancel (arg...)
239		504
240	Temrinates the given process and makes it return the given arguments as	505	Terminates the given Coro and makes it return the given arguments as
241	status (default: the empty list).	506	status (default: the empty list). Never returns if the Coro is the
		507	current Coro.
242		508
243	=cut	509	=cut
244		510
245	sub cancel {	511	sub cancel {
246	my $self = shift;	512	my $self = shift;
		513
		514	if ($current == $self) {
		515	terminate @_;
		516	} else {
247	$self->{status} = [@_];	517	$self->{_status} = [@_];
248	push @destroy, $self;	518	Coro::State::cancel $self;
249	$manager->ready;	519	}
250	&schedule if $current == $self;
251	}	520	}
252		521
		522	=item $coro->schedule_to
		523
		524	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		525	of continuing with the next coro from the ready queue, always switch to
		526	the given coro object (regardless of priority etc.). The readyness
		527	state of that coro isn't changed.
		528
		529	This is an advanced method for special cases - I'd love to hear about any
		530	uses for this one.
		531
		532	=item $coro->cede_to
		533
		534	Like C<schedule_to>, but puts the current coro into the ready
		535	queue. This has the effect of temporarily switching to the given
		536	coro, and continuing some time later.
		537
		538	This is an advanced method for special cases - I'd love to hear about any
		539	uses for this one.
		540
		541	=item $coro->throw ([$scalar])
		542
		543	If C<$throw> is specified and defined, it will be thrown as an exception
		544	inside the coro at the next convenient point in time. Otherwise
		545	clears the exception object.
		546
		547	Coro will check for the exception each time a schedule-like-function
		548	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		549	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		550	detect this case and return early in case an exception is pending.
		551
		552	The exception object will be thrown "as is" with the specified scalar in
		553	C<$@>, i.e. if it is a string, no line number or newline will be appended
		554	(unlike with C<die>).
		555
		556	This can be used as a softer means than C<cancel> to ask a coro to
		557	end itself, although there is no guarantee that the exception will lead to
		558	termination, and if the exception isn't caught it might well end the whole
		559	program.
		560
		561	You might also think of C<throw> as being the moral equivalent of
		562	C<kill>ing a coro with a signal (in this case, a scalar).
		563
253	=item $process->join	564	=item $coro->join
254		565
255	Wait until the coroutine terminates and return any values given to the	566	Wait until the coro terminates and return any values given to the
256	C<terminate> or C<cancel> functions. C<join> can be called multiple times	567	C<terminate> or C<cancel> functions. C<join> can be called concurrently
257	from multiple processes.	568	from multiple coro, and all will be resumed and given the status
		569	return once the C<$coro> terminates.
258		570
259	=cut	571	=cut
260		572
261	sub join {	573	sub join {
262	my $self = shift;	574	my $self = shift;
		575
263	unless ($self->{status}) {	576	unless ($self->{_status}) {
264	push @{$self->{join}}, $current;	577	my $current = $current;
265	&schedule;	578
		579	push @{$self->{_on_destroy}}, sub {
		580	$current->ready;
		581	undef $current;
		582	};
		583
		584	&schedule while $current;
266	}	585	}
		586
267	wantarray ? @{$self->{status}} : $self->{status}[0];	587	wantarray ? @{$self->{_status}} : $self->{_status}[0];
268	}	588	}
269		589
		590	=item $coro->on_destroy (\&cb)
		591
		592	Registers a callback that is called when this coro gets destroyed,
		593	but before it is joined. The callback gets passed the terminate arguments,
		594	if any, and I<must not> die, under any circumstances.
		595
		596	=cut
		597
		598	sub on_destroy {
		599	my ($self, $cb) = @_;
		600
		601	push @{ $self->{_on_destroy} }, $cb;
		602	}
		603
270	=item $oldprio = $process->prio($newprio)	604	=item $oldprio = $coro->prio ($newprio)
271		605
272	Sets (or gets, if the argument is missing) the priority of the	606	Sets (or gets, if the argument is missing) the priority of the
273	process. Higher priority processes get run before lower priority	607	coro. Higher priority coro get run before lower priority
274	processes. Priorities are small signed integers (currently -4 .. +3),	608	coro. Priorities are small signed integers (currently -4 .. +3),
275	that you can refer to using PRIO_xxx constants (use the import tag :prio	609	that you can refer to using PRIO_xxx constants (use the import tag :prio
276	to get then):	610	to get then):
277		611
278	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	612	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
279	3 > 1 > 0 > -1 > -3 > -4	613	3 > 1 > 0 > -1 > -3 > -4
280		614
281	# set priority to HIGH	615	# set priority to HIGH
282	current->prio(PRIO_HIGH);	616	current->prio (PRIO_HIGH);
283		617
284	The idle coroutine ($Coro::idle) always has a lower priority than any	618	The idle coro ($Coro::idle) always has a lower priority than any
285	existing coroutine.	619	existing coro.
286		620
287	Changing the priority of the current process will take effect immediately,	621	Changing the priority of the current coro will take effect immediately,
288	but changing the priority of processes in the ready queue (but not	622	but changing the priority of coro in the ready queue (but not
289	running) will only take effect after the next schedule (of that	623	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.	624	coro). This is a bug that will be fixed in some future version.
291		625
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)	626	=item $newprio = $coro->nice ($change)
301		627
302	Similar to C<prio>, but subtract the given value from the priority (i.e.	628	Similar to C<prio>, but subtract the given value from the priority (i.e.
303	higher values mean lower priority, just as in unix).	629	higher values mean lower priority, just as in unix).
304		630
305	=cut
306
307	sub nice {
308	$_[0]{prio} -= $_[1];
309	}
310
311	=item $olddesc = $process->desc($newdesc)	631	=item $olddesc = $coro->desc ($newdesc)
312		632
313	Sets (or gets in case the argument is missing) the description for this	633	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.	634	coro. This is just a free-form string you can associate with a
		635	coro.
		636
		637	This method simply sets the C<< $coro->{desc} >> member to the given
		638	string. You can modify this member directly if you wish.
315		639
316	=cut	640	=cut
317		641
318	sub desc {	642	sub desc {
319	my $old = $_[0]{desc};	643	my $old = $_[0]{desc};
320	$_[0]{desc} = $_[1] if @_ > 1;	644	$_[0]{desc} = $_[1] if @_ > 1;
321	$old;	645	$old;
322	}	646	}
323		647
		648	sub transfer {
		649	require Carp;
		650	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		651	}
		652
324	=back	653	=back
325		654
		655	=head1 GLOBAL FUNCTIONS
		656
		657	=over 4
		658
		659	=item Coro::nready
		660
		661	Returns the number of coro that are currently in the ready state,
		662	i.e. that can be switched to by calling C<schedule> directory or
		663	indirectly. The value C<0> means that the only runnable coro is the
		664	currently running one, so C<cede> would have no effect, and C<schedule>
		665	would cause a deadlock unless there is an idle handler that wakes up some
		666	coro.
		667
		668	=item my $guard = Coro::guard { ... }
		669
		670	This function still exists, but is deprecated. Please use the
		671	C<Guard::guard> function instead.
		672
		673	=cut
		674
		675	BEGIN { *guard = \&Guard::guard }
		676
		677	=item unblock_sub { ... }
		678
		679	This utility function takes a BLOCK or code reference and "unblocks" it,
		680	returning a new coderef. Unblocking means that calling the new coderef
		681	will return immediately without blocking, returning nothing, while the
		682	original code ref will be called (with parameters) from within another
		683	coro.
		684
		685	The reason this function exists is that many event libraries (such as the
		686	venerable L<Event\|Event> module) are not thread-safe (a weaker form
		687	of reentrancy). This means you must not block within event callbacks,
		688	otherwise you might suffer from crashes or worse. The only event library
		689	currently known that is safe to use without C<unblock_sub> is L<EV>.
		690
		691	This function allows your callbacks to block by executing them in another
		692	coro where it is safe to block. One example where blocking is handy
		693	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		694	disk, for example.
		695
		696	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		697	creating event callbacks that want to block.
		698
		699	If your handler does not plan to block (e.g. simply sends a message to
		700	another coro, or puts some other coro into the ready queue), there is
		701	no reason to use C<unblock_sub>.
		702
		703	Note that you also need to use C<unblock_sub> for any other callbacks that
		704	are indirectly executed by any C-based event loop. For example, when you
		705	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		706	provides callbacks that are the result of some event callback, then you
		707	must not block either, or use C<unblock_sub>.
		708
		709	=cut
		710
		711	our @unblock_queue;
		712
		713	# we create a special coro because we want to cede,
		714	# to reduce pressure on the coro pool (because most callbacks
		715	# return immediately and can be reused) and because we cannot cede
		716	# inside an event callback.
		717	our $unblock_scheduler = new Coro sub {
		718	while () {
		719	while (my $cb = pop @unblock_queue) {
		720	&async_pool (@$cb);
		721
		722	# for short-lived callbacks, this reduces pressure on the coro pool
		723	# as the chance is very high that the async_poll coro will be back
		724	# in the idle state when cede returns
		725	cede;
		726	}
		727	schedule; # sleep well
		728	}
		729	};
		730	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
		731
		732	sub unblock_sub(&) {
		733	my $cb = shift;
		734
		735	sub {
		736	unshift @unblock_queue, [$cb, @_];
		737	$unblock_scheduler->ready;
		738	}
		739	}
		740
		741	=item $cb = Coro::rouse_cb
		742
		743	Create and return a "rouse callback". That's a code reference that,
		744	when called, will remember a copy of its arguments and notify the owner
		745	coro of the callback.
		746
		747	See the next function.
		748
		749	=item @args = Coro::rouse_wait [$cb]
		750
		751	Wait for the specified rouse callback (or the last one that was created in
		752	this coro).
		753
		754	As soon as the callback is invoked (or when the callback was invoked
		755	before C<rouse_wait>), it will return the arguments originally passed to
		756	the rouse callback. In scalar context, that means you get the I<last>
		757	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		758	statement at the end.
		759
		760	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		761
		762	=back
		763
326	=cut	764	=cut
327		765
328	1;	766	1;
329		767
		768	=head1 HOW TO WAIT FOR A CALLBACK
		769
		770	It is very common for a coro to wait for some callback to be
		771	called. This occurs naturally when you use coro in an otherwise
		772	event-based program, or when you use event-based libraries.
		773
		774	These typically register a callback for some event, and call that callback
		775	when the event occured. In a coro, however, you typically want to
		776	just wait for the event, simplyifying things.
		777
		778	For example C<< AnyEvent->child >> registers a callback to be called when
		779	a specific child has exited:
		780
		781	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		782
		783	But from within a coro, you often just want to write this:
		784
		785	my $status = wait_for_child $pid;
		786
		787	Coro offers two functions specifically designed to make this easy,
		788	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		789
		790	The first function, C<rouse_cb>, generates and returns a callback that,
		791	when invoked, will save its arguments and notify the coro that
		792	created the callback.
		793
		794	The second function, C<rouse_wait>, waits for the callback to be called
		795	(by calling C<schedule> to go to sleep) and returns the arguments
		796	originally passed to the callback.
		797
		798	Using these functions, it becomes easy to write the C<wait_for_child>
		799	function mentioned above:
		800
		801	sub wait_for_child($) {
		802	my ($pid) = @_;
		803
		804	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		805
		806	my ($rpid, $rstatus) = Coro::rouse_wait;
		807	$rstatus
		808	}
		809
		810	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		811	you can roll your own, using C<schedule>:
		812
		813	sub wait_for_child($) {
		814	my ($pid) = @_;
		815
		816	# store the current coro in $current,
		817	# and provide result variables for the closure passed to ->child
		818	my $current = $Coro::current;
		819	my ($done, $rstatus);
		820
		821	# pass a closure to ->child
		822	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		823	$rstatus = $_[1]; # remember rstatus
		824	$done = 1; # mark $rstatus as valud
		825	});
		826
		827	# wait until the closure has been called
		828	schedule while !$done;
		829
		830	$rstatus
		831	}
		832
		833
330	=head1 BUGS/LIMITATIONS	834	=head1 BUGS/LIMITATIONS
331		835
332	- you must make very sure that no coro is still active on global	836	=over 4
333	destruction. very bad things might happen otherwise (usually segfaults).
334		837
		838	=item fork with pthread backend
		839
		840	When Coro is compiled using the pthread backend (which isn't recommended
		841	but required on many BSDs as their libcs are completely broken), then
		842	coro will not survive a fork. There is no known workaround except to
		843	fix your libc and use a saner backend.
		844
		845	=item perl process emulation ("threads")
		846
335	- this module is not thread-safe. You should only ever use this module	847	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	848	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	849	future to allow per-thread schedulers, but Coro::State does not yet allow
338	this).	850	this). I recommend disabling thread support and using processes, as having
		851	the windows process emulation enabled under unix roughly halves perl
		852	performance, even when not used.
		853
		854	=item coro switching is not signal safe
		855
		856	You must not switch to another coro from within a signal handler
		857	(only relevant with %SIG - most event libraries provide safe signals).
		858
		859	That means you I<MUST NOT> call any function that might "block" the
		860	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		861	anything that calls those. Everything else, including calling C<ready>,
		862	works.
		863
		864	=back
		865
339		866
340	=head1 SEE ALSO	867	=head1 SEE ALSO
341		868
342	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	869	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>,	870
344	L<Coro::Handle>, L<Coro::RWLock>, L<Coro::Socket>.	871	Debugging: L<Coro::Debug>.
		872
		873	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		874
		875	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		876	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		877
		878	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		879
		880	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		881	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		882	L<Coro::Select>.
		883
		884	XS API: L<Coro::MakeMaker>.
		885
		886	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
345		887
346	=head1 AUTHOR	888	=head1 AUTHOR
347		889
348	Marc Lehmann <pcg@goof.com>	890	Marc Lehmann <schmorp@schmorp.de>
349	http://home.schmorp.de/	891	http://home.schmorp.de/
350		892
351	=cut	893	=cut
352		894

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Revision 1.65 by root, Tue Feb 22 19:51:58 2005 UTC vs.
Revision 1.263 by root, Tue Jul 28 02:04:21 2009 UTC