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…		…
1	NAME	1	NAME
2	Coro - coroutine process abstraction	2	Coro - coroutine process abstraction
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";
		10	cede; # yield back to main
		11	print "4\n";
9	};	12	};
10		13	print "1\n";
11	# alternatively create an async coroutine like this:	14	cede; # yield to coroutine
12		15	print "3\n";
13	sub some_func : Coro {	16	cede; # and again
14	# some more async code
15	}	17
16		18	# use locking
17	cede;	19	my $lock = new Coro::Semaphore;
		20	my $locked;
		21
		22	$lock->down;
		23	$locked = 1;
		24	$lock->up;
18		25
19	DESCRIPTION	26	DESCRIPTION
20	This module collection manages coroutines. Coroutines are similar to	27	This module collection manages coroutines. Coroutines are similar to
21	threads but don't run in parallel at the same time even on SMP machines.	28	threads but don't (in general) run in parallel at the same time even on
22	The specific flavor of coroutine use din this module also guarentees you	29	SMP machines. The specific flavor of coroutine used in this module also
23	that it will not switch between coroutines unless necessary, at	30	guarantees you that it will not switch between coroutines unless
24	easily-identified points in your program, so locking and parallel access	31	necessary, at easily-identified points in your program, so locking and
25	are rarely an issue, making coroutine programming much safer than	32	parallel access are rarely an issue, making coroutine programming much
26	threads programming.	33	safer and easier than threads programming.
27		34
28	(Perl, however, does not natively support real threads but instead does	35	Unlike a normal perl program, however, coroutines allow you to have
29	a very slow and memory-intensive emulation of processes using threads.	36	multiple running interpreters that share data, which is especially
30	This is a performance win on Windows machines, and a loss everywhere	37	useful to code pseudo-parallel processes and for event-based
31	else).	38	programming, such as multiple HTTP-GET requests running concurrently.
		39	See Coro::AnyEvent to learn more.
		40
		41	Coroutines are also useful because Perl has no support for threads (the
		42	so called "threads" that perl offers are nothing more than the (bad)
		43	process emulation coming from the Windows platform: On standard
		44	operating systems they serve no purpose whatsoever, except by making
		45	your programs slow and making them use a lot of memory. Best disable
		46	them when building perl, or aks your software vendor/distributor to do
		47	it for you).
32		48
33	In this module, coroutines are defined as "callchain + lexical variables	49	In this module, coroutines are defined as "callchain + lexical variables
34	+ @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own	50	+ @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own
35	callchain, its own set of lexicals and its own set of perls most	51	callchain, its own set of lexicals and its own set of perls most
36	important global variables.	52	important global variables (see Coro::State for more configuration).
37		53
38	$main	54	$Coro::main
39	This coroutine represents the main program.	55	This variable stores the coroutine object that represents the main
		56	program. While you cna "ready" it and do most other things you can
		57	do to coroutines, it is mainly useful to compare again
		58	$Coro::current, to see wether you are running in the main program or
		59	not.
40		60
41	$current (or as function: current)	61	$Coro::current
42	The current coroutine (the last coroutine switched to). The initial	62	The coroutine object representing the current coroutine (the last
		63	coroutine that the Coro scheduler switched to). The initial value is
43	value is $main (of course).	64	$main (of course).
44		65
45	This variable is strictly read-only. It is provided for	66	This variable is strictly read-only. You can take copies of the
46	performance reasons. If performance is not essentiel you are	67	value stored in it and use it as any other coroutine object, but you
47	encouraged to use the "Coro::current" function instead.	68	must not otherwise modify the variable itself.
48		69
49	$idle	70	$Coro::idle
50	A callback that is called whenever the scheduler finds no ready	71	This variable is mainly useful to integrate Coro into event loops.
51	coroutines to run. The default implementation prints "FATAL:	72	It is usually better to rely on Coro::AnyEvent or L"Coro::EV", as
52	deadlock detected" and exits, because the program has no other way	73	this is pretty low-level functionality.
53	to continue.	74
		75	This variable stores a callback that is called whenever the
		76	scheduler finds no ready coroutines to run. The default
		77	implementation prints "FATAL: deadlock detected" and exits, because
		78	the program has no other way to continue.
54		79
55	This hook is overwritten by modules such as "Coro::Timer" and	80	This hook is overwritten by modules such as "Coro::Timer" and
56	"Coro::Event" to wait on an external event that hopefully wake up a	81	"Coro::AnyEvent" to wait on an external event that hopefully wake up
57	coroutine so the scheduler can run it.	82	a coroutine so the scheduler can run it.
		83
		84	Note that the callback must not, under any circumstances, block
		85	the current coroutine. Normally, this is achieved by having an "idle
		86	coroutine" that calls the event loop and then blocks again, and then
		87	readying that coroutine in the idle handler.
		88
		89	See Coro::Event or Coro::AnyEvent for examples of using this
		90	technique.
58		91
59	Please note that if your callback recursively invokes perl (e.g. for	92	Please note that if your callback recursively invokes perl (e.g. for
60	event handlers), then it must be prepared to be called recursively.	93	event handlers), then it must be prepared to be called recursively
		94	itself.
61		95
62	STATIC METHODS	96	SIMPLE COROUTINE CREATION
63	Static methods are actually functions that operate on the current
64	coroutine only.
65
66	async { ... } [@args...]	97	async { ... } [@args...]
67	Create a new asynchronous coroutine and return it's coroutine object	98	Create a new coroutine and return it's coroutine object (usually
68	(usually unused). When the sub returns the new coroutine is	99	unused). The coroutine will be put into the ready queue, so it will
		100	start running automatically on the next scheduler run.
		101
		102	The first argument is a codeblock/closure that should be executed in
		103	the coroutine. When it returns argument returns the coroutine is
69	automatically terminated.	104	automatically terminated.
70		105
71	Calling "exit" in a coroutine will not work correctly, so do not do	106	The remaining arguments are passed as arguments to the closure.
72	that.
73		107
74	When the coroutine dies, the program will exit, just as in the main	108	See the "Coro::State::new" constructor for info about the coroutine
75	program.	109	environment in which coroutines are executed.
76		110
		111	Calling "exit" in a coroutine will do the same as calling exit
		112	outside the coroutine. Likewise, when the coroutine dies, the
		113	program will exit, just as it would in the main program.
		114
		115	If you do not want that, you can provide a default "die" handler, or
		116	simply avoid dieing (by use of "eval").
		117
77	# create a new coroutine that just prints its arguments	118	Example: Create a new coroutine that just prints its arguments.
		119
78	async {	120	async {
79	print "@_\n";	121	print "@_\n";
80	} 1,2,3,4;	122	} 1,2,3,4;
81		123
82	async_pool { ... } [@args...]	124	async_pool { ... } [@args...]
83	Similar to "async", but uses a coroutine pool, so you should not	125	Similar to "async", but uses a coroutine pool, so you should not
84	call terminate or join (although you are allowed to), and you get a	126	call terminate or join on it (although you are allowed to), and you
85	coroutine that might have executed other code already (which can be	127	get a coroutine that might have executed other code already (which
86	good or bad :).	128	can be good or bad :).
87		129
		130	On the plus side, this function is faster than creating (and
		131	destroying) a completely new coroutine, so if you need a lot of
		132	generic coroutines in quick successsion, use "async_pool", not
		133	"async".
		134
88	Also, the block is executed in an "eval" context and a warning will	135	The code block is executed in an "eval" context and a warning will
89	be issued in case of an exception instead of terminating the	136	be issued in case of an exception instead of terminating the
90	program, as "async" does. As the coroutine is being reused, stuff	137	program, as "async" does. As the coroutine is being reused, stuff
91	like "on_destroy" will not work in the expected way, unless you call	138	like "on_destroy" will not work in the expected way, unless you call
92	terminate or cancel, which somehow defeats the purpose of pooling.	139	terminate or cancel, which somehow defeats the purpose of pooling
		140	(but is fine in the exceptional case).
93		141
94	The priority will be reset to 0 after each job, otherwise the	142	The priority will be reset to 0 after each run, tracing will be
95	coroutine will be re-used "as-is".	143	disabled, the description will be reset and the default output
		144	filehandle gets restored, so you can change all these. Otherwise the
		145	coroutine will be re-used "as-is": most notably if you change other
		146	per-coroutine global stuff such as $/ you must needs to revert
		147	that change, which is most simply done by using local as in: " local
		148	$/ ".
96		149
97	The pool size is limited to 8 idle coroutines (this can be adjusted	150	The pool size is limited to 8 idle coroutines (this can be adjusted
98	by changing $Coro::POOL_SIZE), and there can be as many non-idle	151	by changing $Coro::POOL_SIZE), and there can be as many non-idle
99	coros as required.	152	coros as required.
100		153
101	If you are concerned about pooled coroutines growing a lot because a	154	If you are concerned about pooled coroutines growing a lot because a
102	single "async_pool" used a lot of stackspace you can e.g.	155	single "async_pool" used a lot of stackspace you can e.g.
103	"async_pool { terminate }" once per second or so to slowly replenish	156	"async_pool { terminate }" once per second or so to slowly replenish
104	the pool.	157	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
		159	be destroyed.
		160
		161	STATIC METHODS
		162	Static methods are actually functions that operate on the current
		163	coroutine.
105		164
106	schedule	165	schedule
107	Calls the scheduler. Please note that the current coroutine will not	166	Calls the scheduler. The scheduler will find the next coroutine that
		167	is to be run from the ready queue and switches to it. The next
		168	coroutine to be run is simply the one with the highest priority that
		169	is longest in its ready queue. If there is no coroutine ready, it
		170	will clal the $Coro::idle hook.
		171
		172	Please note that the current coroutine will not be put into the
108	be put into the ready queue, so calling this function usually means	173	ready queue, so calling this function usually means you will never
109	you will never be called again unless something else (e.g. an event	174	be called again unless something else (e.g. an event handler) calls
110	handler) calls ready.	175	"->ready", thus waking you up.
		176
		177	This makes "schedule" the generic method to use to block the
		178	current coroutine and wait for events: first you remember the
		179	current coroutine in a variable, then arrange for some callback of
		180	yours to call "->ready" on that once some event happens, and last
		181	you call "schedule" to put yourself to sleep. Note that a lot of
		182	things can wake your coroutine up, so you need to check wether the
		183	event indeed happened, e.g. by storing the status in a variable.
111		184
112	The canonical way to wait on external events is this:	185	The canonical way to wait on external events is this:
113		186
114	{	187	{
115	# remember current coroutine	188	# remember current coroutine
120	# wake up sleeping coroutine	193	# wake up sleeping coroutine
121	$current->ready;	194	$current->ready;
122	undef $current;	195	undef $current;
123	};	196	};
124		197
125	# call schedule until event occured.	198	# call schedule until event occurred.
126	# in case we are woken up for other reasons	199	# in case we are woken up for other reasons
127	# (current still defined), loop.	200	# (current still defined), loop.
128	Coro::schedule while $current;	201	Coro::schedule while $current;
129	}	202	}
130		203
131	cede	204	cede
132	"Cede" to other coroutines. This function puts the current coroutine	205	"Cede" to other coroutines. This function puts the current coroutine
133	into the ready queue and calls "schedule", which has the effect of	206	into the ready queue and calls "schedule", which has the effect of
134	giving up the current "timeslice" to other coroutines of the same or	207	giving up the current "timeslice" to other coroutines of the same or
135	higher priority.	208	higher priority. Once your coroutine gets its turn again it will
		209	automatically be resumed.
136		210
137	Returns true if at least one coroutine switch has happened.	211	This function is often called "yield" in other languages.
138		212
139	Coro::cede_notself	213	Coro::cede_notself
140	Works like cede, but is not exported by default and will cede to any	214	Works like cede, but is not exported by default and will cede to
141	coroutine, regardless of priority, once.	215	any coroutine, regardless of priority. This is useful sometimes to
142		216	ensure progress is made.
143	Returns true if at least one coroutine switch has happened.
144		217
145	terminate [arg...]	218	terminate [arg...]
146	Terminates the current coroutine with the given status values (see	219	Terminates the current coroutine with the given status values (see
147	cancel).	220	cancel).
148		221
149	# dynamic methods	222	killall
		223	Kills/terminates/cancels all coroutines except the currently running
		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
		227	Note that while this will try to free some of the main programs
		228	resources, you cnanot free all of them, so if a coroutine that is
		229	not the main program calls this function, there will be some
		230	one-time resource leak.
150		231
151	COROUTINE METHODS	232	COROUTINE METHODS
152	These are the methods you can call on coroutine objects.	233	These are the methods you can call on coroutine objects (or to create
		234	them).
153		235
154	new Coro \&sub [, @args...]	236	new Coro \&sub [, @args...]
155	Create a new coroutine and return it. When the sub returns the	237	Create a new coroutine and return it. When the sub returns, the
156	coroutine automatically terminates as if "terminate" with the	238	coroutine automatically terminates as if "terminate" with the
157	returned values were called. To make the coroutine run you must	239	returned values were called. To make the coroutine run you must
158	first put it into the ready queue by calling the ready method.	240	first put it into the ready queue by calling the ready method.
159		241
160	Calling "exit" in a coroutine will not work correctly, so do not do	242	See "async" and "Coro::State::new" for additional info about the
161	that.	243	coroutine environment.
162		244
163	$success = $coroutine->ready	245	$success = $coroutine->ready
164	Put the given coroutine into the ready queue (according to it's	246	Put the given coroutine into the end of its ready queue (there is
165	priority) and return true. If the coroutine is already in the ready	247	one queue for each priority) and return true. If the coroutine is
166	queue, do nothing and return false.	248	already in the ready queue, do nothing and return false.
		249
		250	This ensures that the scheduler will resume this coroutine
		251	automatically once all the coroutines of higher priority and all
		252	coroutines of the same priority that were put into the ready queue
		253	earlier have been resumed.
167		254
168	$is_ready = $coroutine->is_ready	255	$is_ready = $coroutine->is_ready
169	Return wether the coroutine is currently the ready queue or not,	256	Return wether the coroutine is currently the ready queue or not,
170		257
171	$coroutine->cancel (arg...)	258	$coroutine->cancel (arg...)
…		…
173	arguments as status (default: the empty list). Never returns if the	260	arguments as status (default: the empty list). Never returns if the
174	coroutine is the current coroutine.	261	coroutine is the current coroutine.
175		262
176	$coroutine->join	263	$coroutine->join
177	Wait until the coroutine terminates and return any values given to	264	Wait until the coroutine terminates and return any values given to
178	the "terminate" or "cancel" functions. "join" can be called multiple	265	the "terminate" or "cancel" functions. "join" can be called
179	times from multiple coroutine.	266	concurrently from multiple coroutines, and all will be resumed and
		267	given the status return once the $coroutine terminates.
180		268
181	$coroutine->on_destroy (\&cb)	269	$coroutine->on_destroy (\&cb)
182	Registers a callback that is called when this coroutine gets	270	Registers a callback that is called when this coroutine gets
183	destroyed, but before it is joined. The callback gets passed the	271	destroyed, but before it is joined. The callback gets passed the
184	terminate arguments, if any.	272	terminate arguments, if any, and must not die, under any
		273	circumstances.
185		274
186	$oldprio = $coroutine->prio ($newprio)	275	$oldprio = $coroutine->prio ($newprio)
187	Sets (or gets, if the argument is missing) the priority of the	276	Sets (or gets, if the argument is missing) the priority of the
188	coroutine. Higher priority coroutines get run before lower priority	277	coroutine. Higher priority coroutines get run before lower priority
189	coroutines. Priorities are small signed integers (currently -4 ..	278	coroutines. Priorities are small signed integers (currently -4 ..
…		…
212	$olddesc = $coroutine->desc ($newdesc)	301	$olddesc = $coroutine->desc ($newdesc)
213	Sets (or gets in case the argument is missing) the description for	302	Sets (or gets in case the argument is missing) the description for
214	this coroutine. This is just a free-form string you can associate	303	this coroutine. This is just a free-form string you can associate
215	with a coroutine.	304	with a coroutine.
216		305
		306	This method simply sets the "$coroutine->{desc}" member to the given
		307	string. You can modify this member directly if you wish.
		308
		309	$coroutine->throw ([$scalar])
		310	If $throw is specified and defined, it will be thrown as an
		311	exception inside the coroutine at the next convinient point in time
		312	(usually after it gains control at the next schedule/transfer/cede).
		313	Otherwise clears the exception object.
		314
		315	The exception object will be thrown "as is" with the specified
		316	scalar in $@, i.e. if it is a string, no line number or newline will
		317	be appended (unlike with "die").
		318
		319	This can be used as a softer means than "cancel" to ask a coroutine
		320	to end itself, although there is no guarentee that the exception
		321	will lead to termination, and if the exception isn't caught it might
		322	well end the whole program.
		323
217	GLOBAL FUNCTIONS	324	GLOBAL FUNCTIONS
218	Coro::nready	325	Coro::nready
219	Returns the number of coroutines that are currently in the ready	326	Returns the number of coroutines that are currently in the ready
220	state, i.e. that can be swicthed to. The value 0 means that the only	327	state, i.e. that can be switched to by calling "schedule" directory
221	runnable coroutine is the currently running one, so "cede" would	328	or indirectly. The value 0 means that the only runnable coroutine is
222	have no effect, and "schedule" would cause a deadlock unless there	329	the currently running one, so "cede" would have no effect, and
		330	"schedule" would cause a deadlock unless there is an idle handler
223	is an idle handler that wakes up some coroutines.	331	that wakes up some coroutines.
224		332
225	my $guard = Coro::guard { ... }	333	my $guard = Coro::guard { ... }
226	This creates and returns a guard object. Nothing happens until the	334	This creates and returns a guard object. Nothing happens until the
227	objetc gets destroyed, in which case the codeblock given as argument	335	object gets destroyed, in which case the codeblock given as argument
228	will be executed. This is useful to free locks or other resources in	336	will be executed. This is useful to free locks or other resources in
229	case of a runtime error or when the coroutine gets canceled, as in	337	case of a runtime error or when the coroutine gets canceled, as in
230	both cases the guard block will be executed. The guard object	338	both cases the guard block will be executed. The guard object
231	supports only one method, "->cancel", which will keep the codeblock	339	supports only one method, "->cancel", which will keep the codeblock
232	from being executed.	340	from being executed.
…		…
241	# do something that requires $busy to be true	349	# do something that requires $busy to be true
242	}	350	}
243		351
244	unblock_sub { ... }	352	unblock_sub { ... }
245	This utility function takes a BLOCK or code reference and "unblocks"	353	This utility function takes a BLOCK or code reference and "unblocks"
246	it, returning the new coderef. This means that the new coderef will	354	it, returning a new coderef. Unblocking means that calling the new
247	return immediately without blocking, returning nothing, while the	355	coderef will return immediately without blocking, returning nothing,
248	original code ref will be called (with parameters) from within its	356	while the original code ref will be called (with parameters) from
249	own coroutine.	357	within another coroutine.
250		358
251	The reason this fucntion exists is that many event libraries (such	359	The reason this function exists is that many event libraries (such
252	as the venerable Event module) are not coroutine-safe (a weaker form	360	as the venerable Event module) are not coroutine-safe (a weaker form
253	of thread-safety). This means you must not block within event	361	of thread-safety). This means you must not block within event
254	callbacks, otherwise you might suffer from crashes or worse.	362	callbacks, otherwise you might suffer from crashes or worse. The
		363	only event library currently known that is safe to use without
		364	"unblock_sub" is EV.
255		365
256	This function allows your callbacks to block by executing them in	366	This function allows your callbacks to block by executing them in
257	another coroutine where it is safe to block. One example where	367	another coroutine where it is safe to block. One example where
258	blocking is handy is when you use the Coro::AIO functions to save	368	blocking is handy is when you use the Coro::AIO functions to save
259	results to disk.	369	results to disk, for example.
260		370
261	In short: simply use "unblock_sub { ... }" instead of "sub { ... }"	371	In short: simply use "unblock_sub { ... }" instead of "sub { ... }"
262	when creating event callbacks that want to block.	372	when creating event callbacks that want to block.
263		373
		374	If your handler does not plan to block (e.g. simply sends a message
		375	to another coroutine, or puts some other coroutine into the ready
		376	queue), there is no reason to use "unblock_sub".
		377
		378	Note that you also need to use "unblock_sub" for any other callbacks
		379	that are indirectly executed by any C-based event loop. For example,
		380	when you use a module that uses AnyEvent (and you use
		381	Coro::AnyEvent) and it provides callbacks that are the result of
		382	some event callback, then you must not block either, or use
		383	"unblock_sub".
		384
264	BUGS/LIMITATIONS	385	BUGS/LIMITATIONS
265	- you must make very sure that no coro is still active on global
266	destruction. very bad things might happen otherwise (usually segfaults).
267
268	- this module is not thread-safe. You should only ever use this module	386	This module is not perl-pseudo-thread-safe. You should only ever use
269	from the same thread (this requirement might be losened in the future	387	this module from the same thread (this requirement might be removed in
270	to allow per-thread schedulers, but Coro::State does not yet allow	388	the future to allow per-thread schedulers, but Coro::State does not yet
271	this).	389	allow this). I recommend disabling thread support and using processes,
		390	as this is much faster and uses less memory.
272		391
273	SEE ALSO	392	SEE ALSO
		393	Event-Loop integration: Coro::AnyEvent, Coro::EV, Coro::Event.
		394
		395	Debugging: Coro::Debug.
		396
274	Support/Utility: Coro::Cont, Coro::Specific, Coro::State, Coro::Util.	397	Support/Utility: Coro::Specific, Coro::Util.
275		398
276	Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,	399	Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,
277	Coro::SemaphoreSet, Coro::RWLock.	400	Coro::SemaphoreSet, Coro::RWLock.
278		401
279	Event/IO: Coro::Timer, Coro::Event, Coro::Handle, Coro::Socket,	402	IO/Timers: Coro::Timer, Coro::Handle, Coro::Socket, Coro::AIO.
280	Coro::Select.
281		403
282	Embedding: <Coro:MakeMaker>	404	Compatibility: Coro::LWP, Coro::BDB, Coro::Storable, Coro::Select.
		405
		406	XS API: Coro::MakeMaker.
		407
		408	Low level Configuration, Coroutine Environment: Coro::State.
283		409
284	AUTHOR	410	AUTHOR
285	Marc Lehmann <schmorp@schmorp.de>	411	Marc Lehmann <schmorp@schmorp.de>
286	http://home.schmorp.de/	412	http://home.schmorp.de/
287		413

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Comparing Coro/README (file contents): Revision 1.6 by root, Sat Jan 6 02:45:56 2007 UTC vs. Revision 1.14 by root, Sat May 10 22:32:40 2008 UTC

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Comparing Coro/README (file contents):
Revision 1.6 by root, Sat Jan 6 02:45:56 2007 UTC vs.
Revision 1.14 by root, Sat May 10 22:32:40 2008 UTC