[ViewVC] Diff of: cvs/Coro/README

Comparing Coro/README (file contents):
Revision 1.11 by root, Sat Oct 6 19:25:00 2007 UTC vs.
Revision 1.14 by root, Sat May 10 22:32:40 2008 UTC

…		…
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 used in this module also guarantees 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 essential 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
		106	The remaining arguments are passed as arguments to the closure.
		107
71	See the "Coro::State::new" constructor for info about the coroutine	108	See the "Coro::State::new" constructor for info about the coroutine
72	environment.	109	environment in which coroutines are executed.
73		110
74	Calling "exit" in a coroutine will do the same as calling exit	111	Calling "exit" in a coroutine will do the same as calling exit
75	outside the coroutine. Likewise, when the coroutine dies, the	112	outside the coroutine. Likewise, when the coroutine dies, the
76	program will exit, just as it would in the main program.	113	program will exit, just as it would in the main program.
77		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
78	# create a new coroutine that just prints its arguments	118	Example: Create a new coroutine that just prints its arguments.
		119
79	async {	120	async {
80	print "@_\n";	121	print "@_\n";
81	} 1,2,3,4;	122	} 1,2,3,4;
82		123
83	async_pool { ... } [@args...]	124	async_pool { ... } [@args...]
84	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
85	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
86	coroutine that might have executed other code already (which can be	127	get a coroutine that might have executed other code already (which
87	good or bad :).	128	can be good or bad :).
88		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
89	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
90	be issued in case of an exception instead of terminating the	136	be issued in case of an exception instead of terminating the
91	program, as "async" does. As the coroutine is being reused, stuff	137	program, as "async" does. As the coroutine is being reused, stuff
92	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
93	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).
94		141
95	The priority will be reset to 0 after each job, tracing will be	142	The priority will be reset to 0 after each run, tracing will be
96	disabled, the description will be reset and the default output	143	disabled, the description will be reset and the default output
97	filehandle gets restored, so you can change alkl these. Otherwise	144	filehandle gets restored, so you can change all these. Otherwise the
98	the coroutine will be re-used "as-is": most notably if you change	145	coroutine will be re-used "as-is": most notably if you change other
99	other per-coroutine global stuff such as $/ you need to revert that	146	per-coroutine global stuff such as $/ you must needs to revert
100	change, which is most simply done by using local as in " local $/ ".	147	that change, which is most simply done by using local as in: " local
		148	$/ ".
101		149
102	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
103	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
104	coros as required.	152	coros as required.
105		153
106	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
107	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.
108	"async_pool { terminate }" once per second or so to slowly replenish	156	"async_pool { terminate }" once per second or so to slowly replenish
109	the pool. In addition to that, when the stacks used by a handler	157	the pool. In addition to that, when the stacks used by a handler
110	grows larger than 16kb (adjustable with $Coro::POOL_RSS) it will	158	grows larger than 16kb (adjustable via $Coro::POOL_RSS) it will also
111	also exit.	159	be destroyed.
		160
		161	STATIC METHODS
		162	Static methods are actually functions that operate on the current
		163	coroutine.
112		164
113	schedule	165	schedule
114	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
115	be put into the ready queue, so calling this function usually means	173	ready queue, so calling this function usually means you will never
116	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
117	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.
118		184
119	The canonical way to wait on external events is this:	185	The canonical way to wait on external events is this:
120		186
121	{	187	{
122	# remember current coroutine	188	# remember current coroutine
137		203
138	cede	204	cede
139	"Cede" to other coroutines. This function puts the current coroutine	205	"Cede" to other coroutines. This function puts the current coroutine
140	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
141	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
142	higher priority.	208	higher priority. Once your coroutine gets its turn again it will
		209	automatically be resumed.
143		210
144	Returns true if at least one coroutine switch has happened.	211	This function is often called "yield" in other languages.
145		212
146	Coro::cede_notself	213	Coro::cede_notself
147	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
148	coroutine, regardless of priority, once.	215	any coroutine, regardless of priority. This is useful sometimes to
149		216	ensure progress is made.
150	Returns true if at least one coroutine switch has happened.
151		217
152	terminate [arg...]	218	terminate [arg...]
153	Terminates the current coroutine with the given status values (see	219	Terminates the current coroutine with the given status values (see
154	cancel).	220	cancel).
155		221
156	killall	222	killall
157	Kills/terminates/cancels all coroutines except the currently running	223	Kills/terminates/cancels all coroutines except the currently running
158	one. This is useful after a fork, either in the child or the parent,	224	one. This is useful after a fork, either in the child or the parent,
159	as usually only one of them should inherit the running coroutines.	225	as usually only one of them should inherit the running coroutines.
160		226
161	# dynamic methods	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.
162		231
163	COROUTINE METHODS	232	COROUTINE METHODS
164	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).
165		235
166	new Coro \&sub [, @args...]	236	new Coro \&sub [, @args...]
167	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
168	coroutine automatically terminates as if "terminate" with the	238	coroutine automatically terminates as if "terminate" with the
169	returned values were called. To make the coroutine run you must	239	returned values were called. To make the coroutine run you must
170	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.
171		241
172	See "async" and "Coro::State::new" for additional info about the	242	See "async" and "Coro::State::new" for additional info about the
173	coroutine environment.	243	coroutine environment.
174		244
175	$success = $coroutine->ready	245	$success = $coroutine->ready
176	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
177	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
178	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.
179		254
180	$is_ready = $coroutine->is_ready	255	$is_ready = $coroutine->is_ready
181	Return wether the coroutine is currently the ready queue or not,	256	Return wether the coroutine is currently the ready queue or not,
182		257
183	$coroutine->cancel (arg...)	258	$coroutine->cancel (arg...)
…		…
186	coroutine is the current coroutine.	261	coroutine is the current coroutine.
187		262
188	$coroutine->join	263	$coroutine->join
189	Wait until the coroutine terminates and return any values given to	264	Wait until the coroutine terminates and return any values given to
190	the "terminate" or "cancel" functions. "join" can be called	265	the "terminate" or "cancel" functions. "join" can be called
191	concurrently from multiple coroutines.	266	concurrently from multiple coroutines, and all will be resumed and
		267	given the status return once the $coroutine terminates.
192		268
193	$coroutine->on_destroy (\&cb)	269	$coroutine->on_destroy (\&cb)
194	Registers a callback that is called when this coroutine gets	270	Registers a callback that is called when this coroutine gets
195	destroyed, but before it is joined. The callback gets passed the	271	destroyed, but before it is joined. The callback gets passed the
196	terminate arguments, if any.	272	terminate arguments, if any, and must not die, under any
		273	circumstances.
197		274
198	$oldprio = $coroutine->prio ($newprio)	275	$oldprio = $coroutine->prio ($newprio)
199	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
200	coroutine. Higher priority coroutines get run before lower priority	277	coroutine. Higher priority coroutines get run before lower priority
201	coroutines. Priorities are small signed integers (currently -4 ..	278	coroutines. Priorities are small signed integers (currently -4 ..
…		…
245	well end the whole program.	322	well end the whole program.
246		323
247	GLOBAL FUNCTIONS	324	GLOBAL FUNCTIONS
248	Coro::nready	325	Coro::nready
249	Returns the number of coroutines that are currently in the ready	326	Returns the number of coroutines that are currently in the ready
250	state, i.e. that can be switched to. The value 0 means that the only	327	state, i.e. that can be switched to by calling "schedule" directory
251	runnable coroutine is the currently running one, so "cede" would	328	or indirectly. The value 0 means that the only runnable coroutine is
252	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
253	is an idle handler that wakes up some coroutines.	331	that wakes up some coroutines.
254		332
255	my $guard = Coro::guard { ... }	333	my $guard = Coro::guard { ... }
256	This creates and returns a guard object. Nothing happens until the	334	This creates and returns a guard object. Nothing happens until the
257	object gets destroyed, in which case the codeblock given as argument	335	object gets destroyed, in which case the codeblock given as argument
258	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
…		…
271	# do something that requires $busy to be true	349	# do something that requires $busy to be true
272	}	350	}
273		351
274	unblock_sub { ... }	352	unblock_sub { ... }
275	This utility function takes a BLOCK or code reference and "unblocks"	353	This utility function takes a BLOCK or code reference and "unblocks"
276	it, returning the new coderef. This means that the new coderef will	354	it, returning a new coderef. Unblocking means that calling the new
277	return immediately without blocking, returning nothing, while the	355	coderef will return immediately without blocking, returning nothing,
278	original code ref will be called (with parameters) from within its	356	while the original code ref will be called (with parameters) from
279	own coroutine.	357	within another coroutine.
280		358
281	The reason this function exists is that many event libraries (such	359	The reason this function exists is that many event libraries (such
282	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
283	of thread-safety). This means you must not block within event	361	of thread-safety). This means you must not block within event
284	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.
285		365
286	This function allows your callbacks to block by executing them in	366	This function allows your callbacks to block by executing them in
287	another coroutine where it is safe to block. One example where	367	another coroutine where it is safe to block. One example where
288	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
289	results to disk.	369	results to disk, for example.
290		370
291	In short: simply use "unblock_sub { ... }" instead of "sub { ... }"	371	In short: simply use "unblock_sub { ... }" instead of "sub { ... }"
292	when creating event callbacks that want to block.	372	when creating event callbacks that want to block.
293		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
294	BUGS/LIMITATIONS	385	BUGS/LIMITATIONS
295	- you must make very sure that no coro is still active on global
296	destruction. very bad things might happen otherwise (usually segfaults).
297
298	- 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
299	from the same thread (this requirement might be loosened in the future	387	this module from the same thread (this requirement might be removed in
300	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
301	this).	389	allow this). I recommend disabling thread support and using processes,
		390	as this is much faster and uses less memory.
302		391
303	SEE ALSO	392	SEE ALSO
		393	Event-Loop integration: Coro::AnyEvent, Coro::EV, Coro::Event.
		394
		395	Debugging: Coro::Debug.
		396
304	Support/Utility: Coro::Specific, Coro::State, Coro::Util.	397	Support/Utility: Coro::Specific, Coro::Util.
305		398
306	Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,	399	Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,
307	Coro::SemaphoreSet, Coro::RWLock.	400	Coro::SemaphoreSet, Coro::RWLock.
308		401
309	Event/IO: Coro::Timer, Coro::Event, Coro::Handle, Coro::Socket,	402	IO/Timers: Coro::Timer, Coro::Handle, Coro::Socket, Coro::AIO.
310	Coro::Select.
311		403
312	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.
313		409
314	AUTHOR	410	AUTHOR
315	Marc Lehmann <schmorp@schmorp.de>	411	Marc Lehmann <schmorp@schmorp.de>
316	http://home.schmorp.de/	412	http://home.schmorp.de/
317		413

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Comparing Coro/README (file contents): Revision 1.11 by root, Sat Oct 6 19:25:00 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 1.11 by root, Sat Oct 6 19:25:00 2007 UTC vs.
Revision 1.14 by root, Sat May 10 22:32:40 2008 UTC