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1	NAME	1	NAME
2	Coro - coroutine process abstraction	2	Coro - the only real threads in perl
3		3
4	SYNOPSIS	4	SYNOPSIS
5	use Coro;	5	use Coro;
6		6
7	async {	7	async {
8	# some asynchronous thread of execution	8	# some asynchronous thread of execution
9	print "2\n";	9	print "2\n";
10	cede; # yield back to main	10	cede; # yield back to main
11	print "4\n";	11	print "4\n";
12	};	12	};
13	print "1\n";	13	print "1\n";
14	cede; # yield to coroutine	14	cede; # yield to coro
15	print "3\n";	15	print "3\n";
16	cede; # and again	16	cede; # and again
17		17
18	# use locking	18	# use locking
19	use Coro::Semaphore;	19	use Coro::Semaphore;
20	my $lock = new Coro::Semaphore;	20	my $lock = new Coro::Semaphore;
21	my $locked;	21	my $locked;
22		22
23	$lock->down;	23	$lock->down;
24	$locked = 1;	24	$locked = 1;
25	$lock->up;	25	$lock->up;
26		26
27	DESCRIPTION	27	DESCRIPTION
28	This module collection manages coroutines. Coroutines are similar to	28	For a tutorial-style introduction, please read the Coro::Intro manpage.
29	threads but don't (in general) run in parallel at the same time even on	29	This manpage mainly contains reference information.
30	SMP machines. The specific flavor of coroutine used in this module also	30
31	guarantees you that it will not switch between coroutines unless	31	This module collection manages continuations in general, most often in
		32	the form of cooperative threads (also called coros, or simply "coro" in
		33	the documentation). They are similar to kernel threads but don't (in
		34	general) run in parallel at the same time even on SMP machines. The
		35	specific flavor of thread offered by this module also guarantees you
		36	that it will not switch between threads unless necessary, at
32	necessary, at easily-identified points in your program, so locking and	37	easily-identified points in your program, so locking and parallel access
33	parallel access are rarely an issue, making coroutine programming much	38	are rarely an issue, making thread programming much safer and easier
34	safer and easier than threads programming.	39	than using other thread models.
35		40
36	Unlike a normal perl program, however, coroutines allow you to have	41	Unlike the so-called "Perl threads" (which are not actually real threads
37	multiple running interpreters that share data, which is especially	42	but only the windows process emulation ported to unix, and as such act
38	useful to code pseudo-parallel processes and for event-based	43	as processes), Coro provides a full shared address space, which makes
39	programming, such as multiple HTTP-GET requests running concurrently.	44	communication between threads very easy. And Coro's threads are fast,
40	See Coro::AnyEvent to learn more.	45	too: disabling the Windows process emulation code in your perl and using
		46	Coro can easily result in a two to four times speed increase for your
		47	programs. A parallel matrix multiplication benchmark runs over 300 times
		48	faster on a single core than perl's pseudo-threads on a quad core using
		49	all four cores.
41		50
42	Coroutines are also useful because Perl has no support for threads (the	51	Coro achieves that by supporting multiple running interpreters that
43	so called "threads" that perl offers are nothing more than the (bad)	52	share data, which is especially useful to code pseudo-parallel processes
44	process emulation coming from the Windows platform: On standard	53	and for event-based programming, such as multiple HTTP-GET requests
45	operating systems they serve no purpose whatsoever, except by making	54	running concurrently. See Coro::AnyEvent to learn more on how to
46	your programs slow and making them use a lot of memory. Best disable	55	integrate Coro into an event-based environment.
47	them when building perl, or aks your software vendor/distributor to do
48	it for you).
49		56
50	In this module, coroutines are defined as "callchain + lexical variables	57	In this module, a thread is defined as "callchain + lexical variables +
51	+ @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own	58	some package variables + C stack), that is, a thread has its own
52	callchain, its own set of lexicals and its own set of perls most	59	callchain, its own set of lexicals and its own set of perls most
53	important global variables (see Coro::State for more configuration).	60	important global variables (see Coro::State for more configuration and
		61	background info).
54		62
		63	See also the "SEE ALSO" section at the end of this document - the Coro
		64	module family is quite large.
		65
		66	GLOBAL VARIABLES
55	$Coro::main	67	$Coro::main
56	This variable stores the coroutine object that represents the main	68	This variable stores the Coro object that represents the main
57	program. While you cna "ready" it and do most other things you can	69	program. While you cna "ready" it and do most other things you can
58	do to coroutines, it is mainly useful to compare again	70	do to coro, it is mainly useful to compare again $Coro::current, to
59	$Coro::current, to see whether you are running in the main program	71	see whether you are running in the main program or not.
60	or not.
61		72
62	$Coro::current	73	$Coro::current
63	The coroutine object representing the current coroutine (the last	74	The Coro object representing the current coro (the last coro that
64	coroutine that the Coro scheduler switched to). The initial value is	75	the Coro scheduler switched to). The initial value is $Coro::main
65	$main (of course).	76	(of course).
66		77
67	This variable is strictly read-only. You can take copies of the	78	This variable is strictly read-only. You can take copies of the
68	value stored in it and use it as any other coroutine object, but you	79	value stored in it and use it as any other Coro object, but you must
69	must not otherwise modify the variable itself.	80	not otherwise modify the variable itself.
70		81
71	$Coro::idle	82	$Coro::idle
72	This variable is mainly useful to integrate Coro into event loops.	83	This variable is mainly useful to integrate Coro into event loops.
73	It is usually better to rely on Coro::AnyEvent or L"Coro::EV", as	84	It is usually better to rely on Coro::AnyEvent or Coro::EV, as this
74	this is pretty low-level functionality.	85	is pretty low-level functionality.
75		86
76	This variable stores a callback that is called whenever the	87	This variable stores either a Coro object or a callback.
77	scheduler finds no ready coroutines to run. The default
78	implementation prints "FATAL: deadlock detected" and exits, because
79	the program has no other way to continue.
80		88
		89	If it is a callback, the it is called whenever the scheduler finds
		90	no ready coros to run. The default implementation prints "FATAL:
		91	deadlock detected" and exits, because the program has no other way
		92	to continue.
		93
		94	If it is a coro object, then this object will be readied (without
		95	invoking any ready hooks, however) when the scheduler finds no other
		96	ready coros to run.
		97
81	This hook is overwritten by modules such as "Coro::Timer" and	98	This hook is overwritten by modules such as "Coro::EV" and
82	"Coro::AnyEvent" to wait on an external event that hopefully wake up	99	"Coro::AnyEvent" to wait on an external event that hopefully wake up
83	a coroutine so the scheduler can run it.	100	a coro so the scheduler can run it.
84		101
85	Note that the callback must not, under any circumstances, block	102	Note that the callback must not, under any circumstances, block
86	the current coroutine. Normally, this is achieved by having an "idle	103	the current coro. Normally, this is achieved by having an "idle
87	coroutine" that calls the event loop and then blocks again, and then	104	coro" that calls the event loop and then blocks again, and then
88	readying that coroutine in the idle handler.	105	readying that coro in the idle handler, or by simply placing the
		106	idle coro in this variable.
89		107
90	See Coro::Event or Coro::AnyEvent for examples of using this	108	See Coro::Event or Coro::AnyEvent for examples of using this
91	technique.	109	technique.
92		110
93	Please note that if your callback recursively invokes perl (e.g. for	111	Please note that if your callback recursively invokes perl (e.g. for
94	event handlers), then it must be prepared to be called recursively	112	event handlers), then it must be prepared to be called recursively
95	itself.	113	itself.
96		114
97	SIMPLE COROUTINE CREATION	115	SIMPLE CORO CREATION
98	async { ... } [@args...]	116	async { ... } [@args...]
99	Create a new coroutine and return it's coroutine object (usually	117	Create a new coro and return its Coro object (usually unused). The
100	unused). The coroutine will be put into the ready queue, so it will	118	coro will be put into the ready queue, so it will start running
101	start running automatically on the next scheduler run.	119	automatically on the next scheduler run.
102		120
103	The first argument is a codeblock/closure that should be executed in	121	The first argument is a codeblock/closure that should be executed in
104	the coroutine. When it returns argument returns the coroutine is	122	the coro. When it returns argument returns the coro is automatically
105	automatically terminated.	123	terminated.
106		124
107	The remaining arguments are passed as arguments to the closure.	125	The remaining arguments are passed as arguments to the closure.
108		126
109	See the "Coro::State::new" constructor for info about the coroutine	127	See the "Coro::State::new" constructor for info about the coro
110	environment in which coroutines are executed.	128	environment in which coro are executed.
111		129
112	Calling "exit" in a coroutine will do the same as calling exit	130	Calling "exit" in a coro will do the same as calling exit outside
113	outside the coroutine. Likewise, when the coroutine dies, the	131	the coro. Likewise, when the coro dies, the program will exit, just
114	program will exit, just as it would in the main program.	132	as it would in the main program.
115		133
116	If you do not want that, you can provide a default "die" handler, or	134	If you do not want that, you can provide a default "die" handler, or
117	simply avoid dieing (by use of "eval").	135	simply avoid dieing (by use of "eval").
118		136
119	Example: Create a new coroutine that just prints its arguments.	137	Example: Create a new coro that just prints its arguments.
120		138
121	async {	139	async {
122	print "@_\n";	140	print "@_\n";
123	} 1,2,3,4;	141	} 1,2,3,4;
124		142
125	async_pool { ... } [@args...]	143	async_pool { ... } [@args...]
126	Similar to "async", but uses a coroutine pool, so you should not	144	Similar to "async", but uses a coro pool, so you should not call
127	call terminate or join on it (although you are allowed to), and you	145	terminate or join on it (although you are allowed to), and you get a
128	get a coroutine that might have executed other code already (which	146	coro that might have executed other code already (which can be good
129	can be good or bad :).	147	or bad :).
130		148
131	On the plus side, this function is faster than creating (and	149	On the plus side, this function is about twice as fast as creating
132	destroying) a completly new coroutine, so if you need a lot of	150	(and destroying) a completely new coro, so if you need a lot of
133	generic coroutines in quick successsion, use "async_pool", not	151	generic coros in quick successsion, use "async_pool", not "async".
134	"async".
135		152
136	The code block is executed in an "eval" context and a warning will	153	The code block is executed in an "eval" context and a warning will
137	be issued in case of an exception instead of terminating the	154	be issued in case of an exception instead of terminating the
138	program, as "async" does. As the coroutine is being reused, stuff	155	program, as "async" does. As the coro is being reused, stuff like
139	like "on_destroy" will not work in the expected way, unless you call	156	"on_destroy" will not work in the expected way, unless you call
140	terminate or cancel, which somehow defeats the purpose of pooling	157	terminate or cancel, which somehow defeats the purpose of pooling
141	(but is fine in the exceptional case).	158	(but is fine in the exceptional case).
142		159
143	The priority will be reset to 0 after each run, tracing will be	160	The priority will be reset to 0 after each run, tracing will be
144	disabled, the description will be reset and the default output	161	disabled, the description will be reset and the default output
145	filehandle gets restored, so you can change all these. Otherwise the	162	filehandle gets restored, so you can change all these. Otherwise the
146	coroutine will be re-used "as-is": most notably if you change other	163	coro will be re-used "as-is": most notably if you change other
147	per-coroutine global stuff such as $/ you must needs revert that	164	per-coro global stuff such as $/ you must needs revert that
148	change, which is most simply done by using local as in: "local $/".	165	change, which is most simply done by using local as in: "local $/".
149		166
150	The idle pool size is limited to 8 idle coroutines (this can be	167	The idle pool size is limited to 8 idle coros (this can be adjusted
151	adjusted by changing $Coro::POOL_SIZE), but there can be as many	168	by changing $Coro::POOL_SIZE), but there can be as many non-idle
152	non-idle coros as required.	169	coros as required.
153		170
154	If you are concerned about pooled coroutines growing a lot because a	171	If you are concerned about pooled coros growing a lot because a
155	single "async_pool" used a lot of stackspace you can e.g.	172	single "async_pool" used a lot of stackspace you can e.g.
156	"async_pool { terminate }" once per second or so to slowly replenish	173	"async_pool { terminate }" once per second or so to slowly replenish
157	the pool. In addition to that, when the stacks used by a handler	174	the pool. In addition to that, when the stacks used by a handler
158	grows larger than 16kb (adjustable via $Coro::POOL_RSS) it will also	175	grows larger than 32kb (adjustable via $Coro::POOL_RSS) it will also
159	be destroyed.	176	be destroyed.
160		177
161	STATIC METHODS	178	STATIC METHODS
162	Static methods are actually functions that operate on the current	179	Static methods are actually functions that implicitly operate on the
163	coroutine.	180	current coro.
164		181
165	schedule	182	schedule
166	Calls the scheduler. The scheduler will find the next coroutine that	183	Calls the scheduler. The scheduler will find the next coro that is
167	is to be run from the ready queue and switches to it. The next	184	to be run from the ready queue and switches to it. The next coro to
168	coroutine to be run is simply the one with the highest priority that	185	be run is simply the one with the highest priority that is longest
169	is longest in its ready queue. If there is no coroutine ready, it	186	in its ready queue. If there is no coro ready, it will clal the
170	will clal the $Coro::idle hook.	187	$Coro::idle hook.
171		188
172	Please note that the current coroutine will not be put into the	189	Please note that the current coro will not be put into the ready
173	ready queue, so calling this function usually means you will never	190	queue, so calling this function usually means you will never be
174	be called again unless something else (e.g. an event handler) calls	191	called again unless something else (e.g. an event handler) calls
175	"->ready", thus waking you up.	192	"->ready", thus waking you up.
176		193
177	This makes "schedule" the generic method to use to block the	194	This makes "schedule" the generic method to use to block the
178	current coroutine and wait for events: first you remember the	195	current coro and wait for events: first you remember the current
179	current coroutine in a variable, then arrange for some callback of	196	coro in a variable, then arrange for some callback of yours to call
180	yours to call "->ready" on that once some event happens, and last	197	"->ready" on that once some event happens, and last you call
181	you call "schedule" to put yourself to sleep. Note that a lot of	198	"schedule" to put yourself to sleep. Note that a lot of things can
182	things can wake your coroutine up, so you need to check whether the	199	wake your coro up, so you need to check whether the event indeed
183	event indeed happened, e.g. by storing the status in a variable.	200	happened, e.g. by storing the status in a variable.
184		201
185	The canonical way to wait on external events is this:	202	See HOW TO WAIT FOR A CALLBACK, below, for some ways to wait for
186		203	callbacks.
187	{
188	# remember current coroutine
189	my $current = $Coro::current;
190
191	# register a hypothetical event handler
192	on_event_invoke sub {
193	# wake up sleeping coroutine
194	$current->ready;
195	undef $current;
196	};
197
198	# call schedule until event occurred.
199	# in case we are woken up for other reasons
200	# (current still defined), loop.
201	Coro::schedule while $current;
202	}
203		204
204	cede	205	cede
205	"Cede" to other coroutines. This function puts the current coroutine	206	"Cede" to other coros. This function puts the current coro into the
206	into the ready queue and calls "schedule", which has the effect of	207	ready queue and calls "schedule", which has the effect of giving up
207	giving up the current "timeslice" to other coroutines of the same or	208	the current "timeslice" to other coros of the same or higher
208	higher priority. Once your coroutine gets its turn again it will	209	priority. Once your coro gets its turn again it will automatically
209	automatically be resumed.	210	be resumed.
210		211
211	This function is often called "yield" in other languages.	212	This function is often called "yield" in other languages.
212		213
213	Coro::cede_notself	214	Coro::cede_notself
214	Works like cede, but is not exported by default and will cede to	215	Works like cede, but is not exported by default and will cede to
215	any coroutine, regardless of priority. This is useful sometimes to	216	any coro, regardless of priority. This is useful sometimes to
216	ensure progress is made.	217	ensure progress is made.
217		218
218	terminate [arg...]	219	terminate [arg...]
219	Terminates the current coroutine with the given status values (see	220	Terminates the current coro with the given status values (see
220	cancel).	221	cancel).
221		222
		223	Coro::on_enter BLOCK, Coro::on_leave BLOCK
		224	These function install enter and leave winders in the current scope.
		225	The enter block will be executed when on_enter is called and
		226	whenever the current coro is re-entered by the scheduler, while the
		227	leave block is executed whenever the current coro is blocked by the
		228	scheduler, and also when the containing scope is exited (by whatever
		229	means, be it exit, die, last etc.).
		230
		231	*Neither invoking the scheduler, nor exceptions, are allowed within
		232	those BLOCKs*. That means: do not even think about calling "die"
		233	without an eval, and do not even think of entering the scheduler in
		234	any way.
		235
		236	Since both BLOCKs are tied to the current scope, they will
		237	automatically be removed when the current scope exits.
		238
		239	These functions implement the same concept as "dynamic-wind" in
		240	scheme does, and are useful when you want to localise some resource
		241	to a specific coro.
		242
		243	They slow down thread switching considerably for coros that use them
		244	(about 40% for a BLOCK with a single assignment, so thread switching
		245	is still reasonably fast if the handlers are fast).
		246
		247	These functions are best understood by an example: The following
		248	function will change the current timezone to
		249	"Antarctica/South_Pole", which requires a call to "tzset", but by
		250	using "on_enter" and "on_leave", which remember/change the current
		251	timezone and restore the previous value, respectively, the timezone
		252	is only changed for the coro that installed those handlers.
		253
		254	use POSIX qw(tzset);
		255
		256	async {
		257	my $old_tz; # store outside TZ value here
		258
		259	Coro::on_enter {
		260	$old_tz = $ENV{TZ}; # remember the old value
		261
		262	$ENV{TZ} = "Antarctica/South_Pole";
		263	tzset; # enable new value
		264	};
		265
		266	Coro::on_leave {
		267	$ENV{TZ} = $old_tz;
		268	tzset; # restore old value
		269	};
		270
		271	# at this place, the timezone is Antarctica/South_Pole,
		272	# without disturbing the TZ of any other coro.
		273	};
		274
		275	This can be used to localise about any resource (locale, uid,
		276	current working directory etc.) to a block, despite the existance of
		277	other coros.
		278
		279	Another interesting example implements time-sliced multitasking
		280	using interval timers (this could obviously be optimised, but does
		281	the job):
		282
		283	# "timeslice" the given block
		284	sub timeslice(&) {
		285	use Time::HiRes ();
		286
		287	Coro::on_enter {
		288	# on entering the thread, we set an VTALRM handler to cede
		289	$SIG{VTALRM} = sub { cede };
		290	# and then start the interval timer
		291	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		292	};
		293	Coro::on_leave {
		294	# on leaving the thread, we stop the interval timer again
		295	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		296	};
		297
		298	&{+shift};
		299	}
		300
		301	# use like this:
		302	timeslice {
		303	# The following is an endless loop that would normally
		304	# monopolise the process. Since it runs in a timesliced
		305	# environment, it will regularly cede to other threads.
		306	while () { }
		307	};
		308
222	killall	309	killall
223	Kills/terminates/cancels all coroutines except the currently running	310	Kills/terminates/cancels all coros except the currently running one.
224	one. This is useful after a fork, either in the child or the parent,
225	as usually only one of them should inherit the running coroutines.
226		311
227	Note that while this will try to free some of the main programs	312	Note that while this will try to free some of the main interpreter
228	resources, you cannot free all of them, so if a coroutine that is	313	resources if the calling coro isn't the main coro, but one cannot
229	not the main program calls this function, there will be some	314	free all of them, so if a coro that is not the main coro calls this
230	one-time resource leak.	315	function, there will be some one-time resource leak.
231		316
232	COROUTINE METHODS	317	CORO OBJECT METHODS
233	These are the methods you can call on coroutine objects (or to create	318	These are the methods you can call on coro objects (or to create them).
234	them).
235		319
236	new Coro \&sub [, @args...]	320	new Coro \&sub [, @args...]
237	Create a new coroutine and return it. When the sub returns, the	321	Create a new coro and return it. When the sub returns, the coro
238	coroutine automatically terminates as if "terminate" with the	322	automatically terminates as if "terminate" with the returned values
239	returned values were called. To make the coroutine run you must	323	were called. To make the coro run you must first put it into the
240	first put it into the ready queue by calling the ready method.	324	ready queue by calling the ready method.
241		325
242	See "async" and "Coro::State::new" for additional info about the	326	See "async" and "Coro::State::new" for additional info about the
243	coroutine environment.	327	coro environment.
244		328
245	$success = $coroutine->ready	329	$success = $coro->ready
246	Put the given coroutine into the end of its ready queue (there is	330	Put the given coro into the end of its ready queue (there is one
247	one queue for each priority) and return true. If the coroutine is	331	queue for each priority) and return true. If the coro is already in
248	already in the ready queue, do nothing and return false.	332	the ready queue, do nothing and return false.
249		333
250	This ensures that the scheduler will resume this coroutine	334	This ensures that the scheduler will resume this coro automatically
251	automatically once all the coroutines of higher priority and all	335	once all the coro of higher priority and all coro of the same
252	coroutines of the same priority that were put into the ready queue	336	priority that were put into the ready queue earlier have been
253	earlier have been resumed.	337	resumed.
254		338
		339	$coro->suspend
		340	Suspends the specified coro. A suspended coro works just like any
		341	other coro, except that the scheduler will not select a suspended
		342	coro for execution.
		343
		344	Suspending a coro can be useful when you want to keep the coro from
		345	running, but you don't want to destroy it, or when you want to
		346	temporarily freeze a coro (e.g. for debugging) to resume it later.
		347
		348	A scenario for the former would be to suspend all (other) coros
		349	after a fork and keep them alive, so their destructors aren't
		350	called, but new coros can be created.
		351
		352	$coro->resume
		353	If the specified coro was suspended, it will be resumed. Note that
		354	when the coro was in the ready queue when it was suspended, it might
		355	have been unreadied by the scheduler, so an activation might have
		356	been lost.
		357
		358	To avoid this, it is best to put a suspended coro into the ready
		359	queue unconditionally, as every synchronisation mechanism must
		360	protect itself against spurious wakeups, and the one in the Coro
		361	family certainly do that.
		362
255	$is_ready = $coroutine->is_ready	363	$is_ready = $coro->is_ready
256	Return whether the coroutine is currently the ready queue or not,	364	Returns true iff the Coro object is in the ready queue. Unless the
		365	Coro object gets destroyed, it will eventually be scheduled by the
		366	scheduler.
257		367
		368	$is_running = $coro->is_running
		369	Returns true iff the Coro object is currently running. Only one Coro
		370	object can ever be in the running state (but it currently is
		371	possible to have multiple running Coro::States).
		372
		373	$is_suspended = $coro->is_suspended
		374	Returns true iff this Coro object has been suspended. Suspended
		375	Coros will not ever be scheduled.
		376
258	$coroutine->cancel (arg...)	377	$coro->cancel (arg...)
259	Terminates the given coroutine and makes it return the given	378	Terminates the given Coro and makes it return the given arguments as
260	arguments as status (default: the empty list). Never returns if the	379	status (default: the empty list). Never returns if the Coro is the
261	coroutine is the current coroutine.	380	current Coro.
262		381
		382	$coro->schedule_to
		383	Puts the current coro to sleep (like "Coro::schedule"), but instead
		384	of continuing with the next coro from the ready queue, always switch
		385	to the given coro object (regardless of priority etc.). The
		386	readyness state of that coro isn't changed.
		387
		388	This is an advanced method for special cases - I'd love to hear
		389	about any uses for this one.
		390
		391	$coro->cede_to
		392	Like "schedule_to", but puts the current coro into the ready queue.
		393	This has the effect of temporarily switching to the given coro, and
		394	continuing some time later.
		395
		396	This is an advanced method for special cases - I'd love to hear
		397	about any uses for this one.
		398
263	$coroutine->throw ([$scalar])	399	$coro->throw ([$scalar])
264	If $throw is specified and defined, it will be thrown as an	400	If $throw is specified and defined, it will be thrown as an
265	exception inside the coroutine at the next convenient point in time	401	exception inside the coro at the next convenient point in time.
266	(usually after it gains control at the next schedule/transfer/cede).
267	Otherwise clears the exception object.	402	Otherwise clears the exception object.
		403
		404	Coro will check for the exception each time a schedule-like-function
		405	returns, i.e. after each "schedule", "cede",
		406	"Coro::Semaphore->down", "Coro::Handle->readable" and so on. Most of
		407	these functions detect this case and return early in case an
		408	exception is pending.
268		409
269	The exception object will be thrown "as is" with the specified	410	The exception object will be thrown "as is" with the specified
270	scalar in $@, i.e. if it is a string, no line number or newline will	411	scalar in $@, i.e. if it is a string, no line number or newline will
271	be appended (unlike with "die").	412	be appended (unlike with "die").
272		413
273	This can be used as a softer means than "cancel" to ask a coroutine	414	This can be used as a softer means than "cancel" to ask a coro to
274	to end itself, although there is no guarantee that the exception	415	end itself, although there is no guarantee that the exception will
275	will lead to termination, and if the exception isn't caught it might	416	lead to termination, and if the exception isn't caught it might well
276	well end the whole program.	417	end the whole program.
277		418
278	You might also think of "throw" as being the moral equivalent of	419	You might also think of "throw" as being the moral equivalent of
279	"kill"ing a coroutine with a signal (in this case, a scalar).	420	"kill"ing a coro with a signal (in this case, a scalar).
280		421
281	$coroutine->join	422	$coro->join
282	Wait until the coroutine terminates and return any values given to	423	Wait until the coro terminates and return any values given to the
283	the "terminate" or "cancel" functions. "join" can be called	424	"terminate" or "cancel" functions. "join" can be called concurrently
284	concurrently from multiple coroutines, and all will be resumed and	425	from multiple coro, and all will be resumed and given the status
285	given the status return once the $coroutine terminates.	426	return once the $coro terminates.
286		427
287	$coroutine->on_destroy (\&cb)	428	$coro->on_destroy (\&cb)
288	Registers a callback that is called when this coroutine gets	429	Registers a callback that is called when this coro gets destroyed,
289	destroyed, but before it is joined. The callback gets passed the	430	but before it is joined. The callback gets passed the terminate
290	terminate arguments, if any, and must not die, under any	431	arguments, if any, and must not die, under any circumstances.
291	circumstances.
292		432
293	$oldprio = $coroutine->prio ($newprio)	433	$oldprio = $coro->prio ($newprio)
294	Sets (or gets, if the argument is missing) the priority of the	434	Sets (or gets, if the argument is missing) the priority of the coro.
295	coroutine. Higher priority coroutines get run before lower priority	435	Higher priority coro get run before lower priority coro. Priorities
296	coroutines. Priorities are small signed integers (currently -4 ..	436	are small signed integers (currently -4 .. +3), that you can refer
297	+3), that you can refer to using PRIO_xxx constants (use the import	437	to using PRIO_xxx constants (use the import tag :prio to get then):
298	tag :prio to get then):
299		438
300	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	439	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
301	3 > 1 > 0 > -1 > -3 > -4	440	3 > 1 > 0 > -1 > -3 > -4
302		441
303	# set priority to HIGH	442	# set priority to HIGH
304	current->prio(PRIO_HIGH);	443	current->prio (PRIO_HIGH);
305		444
306	The idle coroutine ($Coro::idle) always has a lower priority than	445	The idle coro ($Coro::idle) always has a lower priority than any
307	any existing coroutine.	446	existing coro.
308		447
309	Changing the priority of the current coroutine will take effect	448	Changing the priority of the current coro will take effect
310	immediately, but changing the priority of coroutines in the ready	449	immediately, but changing the priority of coro in the ready queue
311	queue (but not running) will only take effect after the next	450	(but not running) will only take effect after the next schedule (of
312	schedule (of that coroutine). This is a bug that will be fixed in	451	that coro). This is a bug that will be fixed in some future version.
313	some future version.
314		452
315	$newprio = $coroutine->nice ($change)	453	$newprio = $coro->nice ($change)
316	Similar to "prio", but subtract the given value from the priority	454	Similar to "prio", but subtract the given value from the priority
317	(i.e. higher values mean lower priority, just as in unix).	455	(i.e. higher values mean lower priority, just as in unix).
318		456
319	$olddesc = $coroutine->desc ($newdesc)	457	$olddesc = $coro->desc ($newdesc)
320	Sets (or gets in case the argument is missing) the description for	458	Sets (or gets in case the argument is missing) the description for
321	this coroutine. This is just a free-form string you can associate	459	this coro. This is just a free-form string you can associate with a
322	with a coroutine.	460	coro.
323		461
324	This method simply sets the "$coroutine->{desc}" member to the given	462	This method simply sets the "$coro->{desc}" member to the given
325	string. You can modify this member directly if you wish.	463	string. You can modify this member directly if you wish.
326		464
327	GLOBAL FUNCTIONS	465	GLOBAL FUNCTIONS
328	Coro::nready	466	Coro::nready
329	Returns the number of coroutines that are currently in the ready	467	Returns the number of coro that are currently in the ready state,
330	state, i.e. that can be switched to by calling "schedule" directory	468	i.e. that can be switched to by calling "schedule" directory or
331	or indirectly. The value 0 means that the only runnable coroutine is	469	indirectly. The value 0 means that the only runnable coro is the
332	the currently running one, so "cede" would have no effect, and	470	currently running one, so "cede" would have no effect, and
333	"schedule" would cause a deadlock unless there is an idle handler	471	"schedule" would cause a deadlock unless there is an idle handler
334	that wakes up some coroutines.	472	that wakes up some coro.
335		473
336	my $guard = Coro::guard { ... }	474	my $guard = Coro::guard { ... }
337	This creates and returns a guard object. Nothing happens until the	475	This function still exists, but is deprecated. Please use the
338	object gets destroyed, in which case the codeblock given as argument	476	"Guard::guard" function instead.
339	will be executed. This is useful to free locks or other resources in
340	case of a runtime error or when the coroutine gets canceled, as in
341	both cases the guard block will be executed. The guard object
342	supports only one method, "->cancel", which will keep the codeblock
343	from being executed.
344
345	Example: set some flag and clear it again when the coroutine gets
346	canceled or the function returns:
347
348	sub do_something {
349	my $guard = Coro::guard { $busy = 0 };
350	$busy = 1;
351
352	# do something that requires $busy to be true
353	}
354		477
355	unblock_sub { ... }	478	unblock_sub { ... }
356	This utility function takes a BLOCK or code reference and "unblocks"	479	This utility function takes a BLOCK or code reference and "unblocks"
357	it, returning a new coderef. Unblocking means that calling the new	480	it, returning a new coderef. Unblocking means that calling the new
358	coderef will return immediately without blocking, returning nothing,	481	coderef will return immediately without blocking, returning nothing,
359	while the original code ref will be called (with parameters) from	482	while the original code ref will be called (with parameters) from
360	within another coroutine.	483	within another coro.
361		484
362	The reason this function exists is that many event libraries (such	485	The reason this function exists is that many event libraries (such
363	as the venerable Event module) are not coroutine-safe (a weaker form	486	as the venerable Event module) are not thread-safe (a weaker form of
364	of thread-safety). This means you must not block within event	487	reentrancy). This means you must not block within event callbacks,
365	callbacks, otherwise you might suffer from crashes or worse. The	488	otherwise you might suffer from crashes or worse. The only event
366	only event library currently known that is safe to use without	489	library currently known that is safe to use without "unblock_sub" is
367	"unblock_sub" is EV.	490	EV.
368		491
369	This function allows your callbacks to block by executing them in	492	This function allows your callbacks to block by executing them in
370	another coroutine where it is safe to block. One example where	493	another coro where it is safe to block. One example where blocking
371	blocking is handy is when you use the Coro::AIO functions to save	494	is handy is when you use the Coro::AIO functions to save results to
372	results to disk, for example.	495	disk, for example.
373		496
374	In short: simply use "unblock_sub { ... }" instead of "sub { ... }"	497	In short: simply use "unblock_sub { ... }" instead of "sub { ... }"
375	when creating event callbacks that want to block.	498	when creating event callbacks that want to block.
376		499
377	If your handler does not plan to block (e.g. simply sends a message	500	If your handler does not plan to block (e.g. simply sends a message
378	to another coroutine, or puts some other coroutine into the ready	501	to another coro, or puts some other coro into the ready queue),
379	queue), there is no reason to use "unblock_sub".	502	there is no reason to use "unblock_sub".
380		503
381	Note that you also need to use "unblock_sub" for any other callbacks	504	Note that you also need to use "unblock_sub" for any other callbacks
382	that are indirectly executed by any C-based event loop. For example,	505	that are indirectly executed by any C-based event loop. For example,
383	when you use a module that uses AnyEvent (and you use	506	when you use a module that uses AnyEvent (and you use
384	Coro::AnyEvent) and it provides callbacks that are the result of	507	Coro::AnyEvent) and it provides callbacks that are the result of
385	some event callback, then you must not block either, or use	508	some event callback, then you must not block either, or use
386	"unblock_sub".	509	"unblock_sub".
387		510
		511	$cb = Coro::rouse_cb
		512	Create and return a "rouse callback". That's a code reference that,
		513	when called, will remember a copy of its arguments and notify the
		514	owner coro of the callback.
		515
		516	See the next function.
		517
		518	@args = Coro::rouse_wait [$cb]
		519	Wait for the specified rouse callback (or the last one that was
		520	created in this coro).
		521
		522	As soon as the callback is invoked (or when the callback was invoked
		523	before "rouse_wait"), it will return the arguments originally passed
		524	to the rouse callback. In scalar context, that means you get the
		525	last argument, just as if "rouse_wait" had a "return ($a1, $a2,
		526	$a3...)" statement at the end.
		527
		528	See the section HOW TO WAIT FOR A CALLBACK for an actual usage
		529	example.
		530
		531	HOW TO WAIT FOR A CALLBACK
		532	It is very common for a coro to wait for some callback to be called.
		533	This occurs naturally when you use coro in an otherwise event-based
		534	program, or when you use event-based libraries.
		535
		536	These typically register a callback for some event, and call that
		537	callback when the event occured. In a coro, however, you typically want
		538	to just wait for the event, simplyifying things.
		539
		540	For example "AnyEvent->child" registers a callback to be called when a
		541	specific child has exited:
		542
		543	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		544
		545	But from within a coro, you often just want to write this:
		546
		547	my $status = wait_for_child $pid;
		548
		549	Coro offers two functions specifically designed to make this easy,
		550	"Coro::rouse_cb" and "Coro::rouse_wait".
		551
		552	The first function, "rouse_cb", generates and returns a callback that,
		553	when invoked, will save its arguments and notify the coro that created
		554	the callback.
		555
		556	The second function, "rouse_wait", waits for the callback to be called
		557	(by calling "schedule" to go to sleep) and returns the arguments
		558	originally passed to the callback.
		559
		560	Using these functions, it becomes easy to write the "wait_for_child"
		561	function mentioned above:
		562
		563	sub wait_for_child($) {
		564	my ($pid) = @_;
		565
		566	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		567
		568	my ($rpid, $rstatus) = Coro::rouse_wait;
		569	$rstatus
		570	}
		571
		572	In the case where "rouse_cb" and "rouse_wait" are not flexible enough,
		573	you can roll your own, using "schedule":
		574
		575	sub wait_for_child($) {
		576	my ($pid) = @_;
		577
		578	# store the current coro in $current,
		579	# and provide result variables for the closure passed to ->child
		580	my $current = $Coro::current;
		581	my ($done, $rstatus);
		582
		583	# pass a closure to ->child
		584	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		585	$rstatus = $_[1]; # remember rstatus
		586	$done = 1; # mark $rstatus as valud
		587	});
		588
		589	# wait until the closure has been called
		590	schedule while !$done;
		591
		592	$rstatus
		593	}
		594
388	BUGS/LIMITATIONS	595	BUGS/LIMITATIONS
		596	fork with pthread backend
		597	When Coro is compiled using the pthread backend (which isn't
		598	recommended but required on many BSDs as their libcs are completely
		599	broken), then coro will not survive a fork. There is no known
		600	workaround except to fix your libc and use a saner backend.
		601
		602	perl process emulation ("threads")
389	This module is not perl-pseudo-thread-safe. You should only ever use	603	This module is not perl-pseudo-thread-safe. You should only ever use
390	this module from the same thread (this requirement might be removed in	604	this module from the first thread (this requirement might be removed
391	the future to allow per-thread schedulers, but Coro::State does not yet	605	in the future to allow per-thread schedulers, but Coro::State does
392	allow this). I recommend disabling thread support and using processes,	606	not yet allow this). I recommend disabling thread support and using
393	as this is much faster and uses less memory.	607	processes, as having the windows process emulation enabled under
		608	unix roughly halves perl performance, even when not used.
		609
		610	coro switching is not signal safe
		611	You must not switch to another coro from within a signal handler
		612	(only relevant with %SIG - most event libraries provide safe
		613	signals).
		614
		615	That means you MUST NOT call any function that might "block" the
		616	current coro - "cede", "schedule" "Coro::Semaphore->down" or
		617	anything that calls those. Everything else, including calling
		618	"ready", works.
394		619
395	SEE ALSO	620	SEE ALSO
396	Event-Loop integration: Coro::AnyEvent, Coro::EV, Coro::Event.	621	Event-Loop integration: Coro::AnyEvent, Coro::EV, Coro::Event.
397		622
398	Debugging: Coro::Debug.	623	Debugging: Coro::Debug.
399		624
400	Support/Utility: Coro::Specific, Coro::Util.	625	Support/Utility: Coro::Specific, Coro::Util.
401		626
402	Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,	627	Locking and IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,
403	Coro::SemaphoreSet, Coro::RWLock.	628	Coro::SemaphoreSet, Coro::RWLock.
404		629
405	IO/Timers: Coro::Timer, Coro::Handle, Coro::Socket, Coro::AIO.	630	I/O and Timers: Coro::Timer, Coro::Handle, Coro::Socket, Coro::AIO.
406		631
407	Compatibility: Coro::LWP, Coro::BDB, Coro::Storable, Coro::Select.	632	Compatibility with other modules: Coro::LWP (but see also AnyEvent::HTTP
		633	for a better-working alternative), Coro::BDB, Coro::Storable,
		634	Coro::Select.
408		635
409	XS API: Coro::MakeMaker.	636	XS API: Coro::MakeMaker.
410		637
411	Low level Configuration, Coroutine Environment: Coro::State.	638	Low level Configuration, Thread Environment, Continuations: Coro::State.
412		639
413	AUTHOR	640	AUTHOR
414	Marc Lehmann <schmorp@schmorp.de>	641	Marc Lehmann <schmorp@schmorp.de>
415	http://home.schmorp.de/	642	http://home.schmorp.de/
416		643

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Revision 1.25 by root, Tue Jun 30 08:28:55 2009 UTC