[ViewVC] Diff of: cvs/Coro/README

Comparing Coro/README (file contents):
Revision 1.2 by root, Sat Aug 20 01:10:22 2005 UTC vs.
Revision 1.15 by root, Sun Sep 21 01:23:26 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 process 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	use Coro::Semaphore;
		20	my $lock = new Coro::Semaphore;
		21	my $locked;
		22
		23	$lock->down;
		24	$locked = 1;
		25	$lock->up;
18		26
19	DESCRIPTION	27	DESCRIPTION
20	This module collection manages coroutines. Coroutines are similar to	28	This module collection manages coroutines. Coroutines are similar to
21	threads but don't run in parallel.	29	threads but don't (in general) run in parallel at the same time even on
		30	SMP machines. The specific flavor of coroutine used in this module also
		31	guarantees you that it will not switch between coroutines unless
		32	necessary, at easily-identified points in your program, so locking and
		33	parallel access are rarely an issue, making coroutine programming much
		34	safer and easier than threads programming.
		35
		36	Unlike a normal perl program, however, coroutines allow you to have
		37	multiple running interpreters that share data, which is especially
		38	useful to code pseudo-parallel processes and for event-based
		39	programming, such as multiple HTTP-GET requests running concurrently.
		40	See Coro::AnyEvent to learn more.
		41
		42	Coroutines are also useful because Perl has no support for threads (the
		43	so called "threads" that perl offers are nothing more than the (bad)
		44	process emulation coming from the Windows platform: On standard
		45	operating systems they serve no purpose whatsoever, except by making
		46	your programs slow and making them use a lot of memory. Best disable
		47	them when building perl, or aks your software vendor/distributor to do
		48	it for you).
22		49
23	In this module, coroutines are defined as "callchain + lexical variables	50	In this module, coroutines are defined as "callchain + lexical variables
24	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own	51	+ @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own
25	callchain, it's own set of lexicals and it's own set of perl's most	52	callchain, its own set of lexicals and its own set of perls most
26	important global variables.	53	important global variables (see Coro::State for more configuration).
27		54
28	$main	55	$Coro::main
29	This coroutine represents the main program.	56	This variable stores the coroutine object that represents the main
		57	program. While you cna "ready" it and do most other things you can
		58	do to coroutines, it is mainly useful to compare again
		59	$Coro::current, to see whether you are running in the main program
		60	or not.
30		61
31	$current (or as function: current)	62	$Coro::current
32	The current coroutine (the last coroutine switched to). The initial	63	The coroutine object representing the current coroutine (the last
		64	coroutine that the Coro scheduler switched to). The initial value is
33	value is $main (of course).	65	$main (of course).
34		66
		67	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
		69	must not otherwise modify the variable itself.
		70
35	$idle	71	$Coro::idle
36	The coroutine to switch to when no other coroutine is running. The	72	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
		74	this is pretty low-level functionality.
		75
		76	This variable stores a callback that is called whenever the
		77	scheduler finds no ready coroutines to run. The default
37	default implementation prints "FATAL: deadlock detected" and exits.	78	implementation prints "FATAL: deadlock detected" and exits, because
		79	the program has no other way to continue.
38		80
39	STATIC METHODS	81	This hook is overwritten by modules such as "Coro::Timer" and
40	Static methods are actually functions that operate on the current	82	"Coro::AnyEvent" to wait on an external event that hopefully wake up
41	process only.	83	a coroutine so the scheduler can run it.
42		84
		85	Note that the callback must not, under any circumstances, block
		86	the current coroutine. Normally, this is achieved by having an "idle
		87	coroutine" that calls the event loop and then blocks again, and then
		88	readying that coroutine in the idle handler.
		89
		90	See Coro::Event or Coro::AnyEvent for examples of using this
		91	technique.
		92
		93	Please note that if your callback recursively invokes perl (e.g. for
		94	event handlers), then it must be prepared to be called recursively
		95	itself.
		96
		97	SIMPLE COROUTINE CREATION
43	async { ... } [@args...]	98	async { ... } [@args...]
44	Create a new asynchronous process and return it's process object	99	Create a new coroutine and return it's coroutine object (usually
45	(usually unused). When the sub returns the new process is	100	unused). The coroutine will be put into the ready queue, so it will
		101	start running automatically on the next scheduler run.
		102
		103	The first argument is a codeblock/closure that should be executed in
		104	the coroutine. When it returns argument returns the coroutine is
46	automatically terminated.	105	automatically terminated.
47		106
		107	The remaining arguments are passed as arguments to the closure.
		108
		109	See the "Coro::State::new" constructor for info about the coroutine
		110	environment in which coroutines are executed.
		111
		112	Calling "exit" in a coroutine will do the same as calling exit
		113	outside the coroutine. Likewise, when the coroutine dies, the
		114	program will exit, just as it would in the main program.
		115
		116	If you do not want that, you can provide a default "die" handler, or
		117	simply avoid dieing (by use of "eval").
		118
48	# create a new coroutine that just prints its arguments	119	Example: Create a new coroutine that just prints its arguments.
		120
49	async {	121	async {
50	print "@_\n";	122	print "@_\n";
51	} 1,2,3,4;	123	} 1,2,3,4;
52		124
		125	async_pool { ... } [@args...]
		126	Similar to "async", but uses a coroutine pool, so you should not
		127	call terminate or join on it (although you are allowed to), and you
		128	get a coroutine that might have executed other code already (which
		129	can be good or bad :).
		130
		131	On the plus side, this function is faster than creating (and
		132	destroying) a completely new coroutine, so if you need a lot of
		133	generic coroutines in quick successsion, use "async_pool", not
		134	"async".
		135
		136	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
		138	program, as "async" does. As the coroutine is being reused, stuff
		139	like "on_destroy" will not work in the expected way, unless you call
		140	terminate or cancel, which somehow defeats the purpose of pooling
		141	(but is fine in the exceptional case).
		142
		143	The priority will be reset to 0 after each run, tracing will be
		144	disabled, the description will be reset and the default output
		145	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
		147	per-coroutine global stuff such as $/ you must needs to revert
		148	that change, which is most simply done by using local as in: " local
		149	$/ ".
		150
		151	The pool size is limited to 8 idle coroutines (this can be adjusted
		152	by changing $Coro::POOL_SIZE), and there can be as many non-idle
		153	coros as required.
		154
		155	If you are concerned about pooled coroutines growing a lot because a
		156	single "async_pool" used a lot of stackspace you can e.g.
		157	"async_pool { terminate }" once per second or so to slowly replenish
		158	the pool. In addition to that, when the stacks used by a handler
		159	grows larger than 16kb (adjustable via $Coro::POOL_RSS) it will also
		160	be destroyed.
		161
		162	STATIC METHODS
		163	Static methods are actually functions that operate on the current
		164	coroutine.
		165
53	schedule	166	schedule
54	Calls the scheduler. Please note that the current process will not	167	Calls the scheduler. The scheduler will find the next coroutine that
		168	is to be run from the ready queue and switches to it. The next
		169	coroutine to be run is simply the one with the highest priority that
		170	is longest in its ready queue. If there is no coroutine ready, it
		171	will clal the $Coro::idle hook.
		172
		173	Please note that the current coroutine will not be put into the
55	be put into the ready queue, so calling this function usually means	174	ready queue, so calling this function usually means you will never
56	you will never be called again.	175	be called again unless something else (e.g. an event handler) calls
		176	"->ready", thus waking you up.
		177
		178	This makes "schedule" the generic method to use to block the
		179	current coroutine and wait for events: first you remember the
		180	current coroutine in a variable, then arrange for some callback of
		181	yours to call "->ready" on that once some event happens, and last
		182	you call "schedule" to put yourself to sleep. Note that a lot of
		183	things can wake your coroutine up, so you need to check whether the
		184	event indeed happened, e.g. by storing the status in a variable.
		185
		186	The canonical way to wait on external events is this:
		187
		188	{
		189	# remember current coroutine
		190	my $current = $Coro::current;
		191
		192	# register a hypothetical event handler
		193	on_event_invoke sub {
		194	# wake up sleeping coroutine
		195	$current->ready;
		196	undef $current;
		197	};
		198
		199	# call schedule until event occurred.
		200	# in case we are woken up for other reasons
		201	# (current still defined), loop.
		202	Coro::schedule while $current;
		203	}
57		204
58	cede	205	cede
59	"Cede" to other processes. This function puts the current process	206	"Cede" to other coroutines. This function puts the current coroutine
60	into the ready queue and calls "schedule", which has the effect of	207	into the ready queue and calls "schedule", which has the effect of
61	giving up the current "timeslice" to other coroutines of the same or	208	giving up the current "timeslice" to other coroutines of the same or
62	higher priority.	209	higher priority. Once your coroutine gets its turn again it will
		210	automatically be resumed.
		211
		212	This function is often called "yield" in other languages.
		213
		214	Coro::cede_notself
		215	Works like cede, but is not exported by default and will cede to
		216	any coroutine, regardless of priority. This is useful sometimes to
		217	ensure progress is made.
63		218
64	terminate [arg...]	219	terminate [arg...]
65	Terminates the current process with the given status values (see	220	Terminates the current coroutine with the given status values (see
66	cancel).	221	cancel).
67		222
68	# dynamic methods	223	killall
		224	Kills/terminates/cancels all coroutines except the currently running
		225	one. This is useful after a fork, either in the child or the parent,
		226	as usually only one of them should inherit the running coroutines.
69		227
70	PROCESS METHODS	228	Note that while this will try to free some of the main programs
		229	resources, you cannot free all of them, so if a coroutine that is
		230	not the main program calls this function, there will be some
		231	one-time resource leak.
		232
		233	COROUTINE METHODS
71	These are the methods you can call on process objects.	234	These are the methods you can call on coroutine objects (or to create
		235	them).
72		236
73	new Coro \&sub [, @args...]	237	new Coro \&sub [, @args...]
74	Create a new process and return it. When the sub returns the process	238	Create a new coroutine and return it. When the sub returns, the
75	automatically terminates as if "terminate" with the returned values	239	coroutine automatically terminates as if "terminate" with the
76	were called. To make the process run you must first put it into the	240	returned values were called. To make the coroutine run you must
77	ready queue by calling the ready method.	241	first put it into the ready queue by calling the ready method.
78		242
79	$process->ready	243	See "async" and "Coro::State::new" for additional info about the
80	Put the given process into the ready queue.	244	coroutine environment.
81		245
		246	$success = $coroutine->ready
		247	Put the given coroutine into the end of its ready queue (there is
		248	one queue for each priority) and return true. If the coroutine is
		249	already in the ready queue, do nothing and return false.
		250
		251	This ensures that the scheduler will resume this coroutine
		252	automatically once all the coroutines of higher priority and all
		253	coroutines of the same priority that were put into the ready queue
		254	earlier have been resumed.
		255
		256	$is_ready = $coroutine->is_ready
		257	Return whether the coroutine is currently the ready queue or not,
		258
82	$process->cancel (arg...)	259	$coroutine->cancel (arg...)
83	Temrinates the given process and makes it return the given arguments	260	Terminates the given coroutine and makes it return the given
84	as status (default: the empty list).	261	arguments as status (default: the empty list). Never returns if the
		262	coroutine is the current coroutine.
85		263
86	$process->join	264	$coroutine->join
87	Wait until the coroutine terminates and return any values given to	265	Wait until the coroutine terminates and return any values given to
88	the "terminate" or "cancel" functions. "join" can be called multiple	266	the "terminate" or "cancel" functions. "join" can be called
89	times from multiple processes.	267	concurrently from multiple coroutines, and all will be resumed and
		268	given the status return once the $coroutine terminates.
90		269
		270	$coroutine->on_destroy (\&cb)
		271	Registers a callback that is called when this coroutine gets
		272	destroyed, but before it is joined. The callback gets passed the
		273	terminate arguments, if any, and must not die, under any
		274	circumstances.
		275
91	$oldprio = $process->prio($newprio)	276	$oldprio = $coroutine->prio ($newprio)
92	Sets (or gets, if the argument is missing) the priority of the	277	Sets (or gets, if the argument is missing) the priority of the
93	process. Higher priority processes get run before lower priority	278	coroutine. Higher priority coroutines get run before lower priority
94	processes. Priorities are small signed integers (currently -4 ..	279	coroutines. Priorities are small signed integers (currently -4 ..
95	+3), that you can refer to using PRIO_xxx constants (use the import	280	+3), that you can refer to using PRIO_xxx constants (use the import
96	tag :prio to get then):	281	tag :prio to get then):
97		282
98	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	283	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
99	3 > 1 > 0 > -1 > -3 > -4	284	3 > 1 > 0 > -1 > -3 > -4
102	current->prio(PRIO_HIGH);	287	current->prio(PRIO_HIGH);
103		288
104	The idle coroutine ($Coro::idle) always has a lower priority than	289	The idle coroutine ($Coro::idle) always has a lower priority than
105	any existing coroutine.	290	any existing coroutine.
106		291
107	Changing the priority of the current process will take effect	292	Changing the priority of the current coroutine will take effect
108	immediately, but changing the priority of processes in the ready	293	immediately, but changing the priority of coroutines in the ready
109	queue (but not running) will only take effect after the next	294	queue (but not running) will only take effect after the next
110	schedule (of that process). This is a bug that will be fixed in some	295	schedule (of that coroutine). This is a bug that will be fixed in
111	future version.	296	some future version.
112		297
113	$newprio = $process->nice($change)	298	$newprio = $coroutine->nice ($change)
114	Similar to "prio", but subtract the given value from the priority	299	Similar to "prio", but subtract the given value from the priority
115	(i.e. higher values mean lower priority, just as in unix).	300	(i.e. higher values mean lower priority, just as in unix).
116		301
117	$olddesc = $process->desc($newdesc)	302	$olddesc = $coroutine->desc ($newdesc)
118	Sets (or gets in case the argument is missing) the description for	303	Sets (or gets in case the argument is missing) the description for
119	this process. This is just a free-form string you can associate with	304	this coroutine. This is just a free-form string you can associate
120	a process.	305	with a coroutine.
		306
		307	This method simply sets the "$coroutine->{desc}" member to the given
		308	string. You can modify this member directly if you wish.
		309
		310	$coroutine->throw ([$scalar])
		311	If $throw is specified and defined, it will be thrown as an
		312	exception inside the coroutine at the next convinient point in time
		313	(usually after it gains control at the next schedule/transfer/cede).
		314	Otherwise clears the exception object.
		315
		316	The exception object will be thrown "as is" with the specified
		317	scalar in $@, i.e. if it is a string, no line number or newline will
		318	be appended (unlike with "die").
		319
		320	This can be used as a softer means than "cancel" to ask a coroutine
		321	to end itself, although there is no guarentee that the exception
		322	will lead to termination, and if the exception isn't caught it might
		323	well end the whole program.
		324
		325	GLOBAL FUNCTIONS
		326	Coro::nready
		327	Returns the number of coroutines that are currently in the ready
		328	state, i.e. that can be switched to by calling "schedule" directory
		329	or indirectly. The value 0 means that the only runnable coroutine is
		330	the currently running one, so "cede" would have no effect, and
		331	"schedule" would cause a deadlock unless there is an idle handler
		332	that wakes up some coroutines.
		333
		334	my $guard = Coro::guard { ... }
		335	This creates and returns a guard object. Nothing happens until the
		336	object gets destroyed, in which case the codeblock given as argument
		337	will be executed. This is useful to free locks or other resources in
		338	case of a runtime error or when the coroutine gets canceled, as in
		339	both cases the guard block will be executed. The guard object
		340	supports only one method, "->cancel", which will keep the codeblock
		341	from being executed.
		342
		343	Example: set some flag and clear it again when the coroutine gets
		344	canceled or the function returns:
		345
		346	sub do_something {
		347	my $guard = Coro::guard { $busy = 0 };
		348	$busy = 1;
		349
		350	# do something that requires $busy to be true
		351	}
		352
		353	unblock_sub { ... }
		354	This utility function takes a BLOCK or code reference and "unblocks"
		355	it, returning a new coderef. Unblocking means that calling the new
		356	coderef will return immediately without blocking, returning nothing,
		357	while the original code ref will be called (with parameters) from
		358	within another coroutine.
		359
		360	The reason this function exists is that many event libraries (such
		361	as the venerable Event module) are not coroutine-safe (a weaker form
		362	of thread-safety). This means you must not block within event
		363	callbacks, otherwise you might suffer from crashes or worse. The
		364	only event library currently known that is safe to use without
		365	"unblock_sub" is EV.
		366
		367	This function allows your callbacks to block by executing them in
		368	another coroutine where it is safe to block. One example where
		369	blocking is handy is when you use the Coro::AIO functions to save
		370	results to disk, for example.
		371
		372	In short: simply use "unblock_sub { ... }" instead of "sub { ... }"
		373	when creating event callbacks that want to block.
		374
		375	If your handler does not plan to block (e.g. simply sends a message
		376	to another coroutine, or puts some other coroutine into the ready
		377	queue), there is no reason to use "unblock_sub".
		378
		379	Note that you also need to use "unblock_sub" for any other callbacks
		380	that are indirectly executed by any C-based event loop. For example,
		381	when you use a module that uses AnyEvent (and you use
		382	Coro::AnyEvent) and it provides callbacks that are the result of
		383	some event callback, then you must not block either, or use
		384	"unblock_sub".
121		385
122	BUGS/LIMITATIONS	386	BUGS/LIMITATIONS
123	- you must make very sure that no coro is still active on global
124	destruction. very bad things might happen otherwise (usually segfaults).
125
126	- this module is not thread-safe. You should only ever use this module	387	This module is not perl-pseudo-thread-safe. You should only ever use
127	from the same thread (this requirement might be losened in the future	388	this module from the same thread (this requirement might be removed in
128	to allow per-thread schedulers, but Coro::State does not yet allow	389	the future to allow per-thread schedulers, but Coro::State does not yet
129	this).	390	allow this). I recommend disabling thread support and using processes,
		391	as this is much faster and uses less memory.
130		392
131	SEE ALSO	393	SEE ALSO
		394	Event-Loop integration: Coro::AnyEvent, Coro::EV, Coro::Event.
		395
		396	Debugging: Coro::Debug.
		397
132	Support/Utility: Coro::Cont, Coro::Specific, Coro::State, Coro::Util.	398	Support/Utility: Coro::Specific, Coro::Util.
133		399
134	Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,	400	Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,
135	Coro::SemaphoreSet, Coro::RWLock.	401	Coro::SemaphoreSet, Coro::RWLock.
136		402
137	Event/IO: Coro::Timer, Coro::Event, Coro::Handle, Coro::Socket,	403	IO/Timers: Coro::Timer, Coro::Handle, Coro::Socket, Coro::AIO.
138	Coro::Select.
139		404
140	Embedding: <Coro:MakeMaker>	405	Compatibility: Coro::LWP, Coro::BDB, Coro::Storable, Coro::Select.
		406
		407	XS API: Coro::MakeMaker.
		408
		409	Low level Configuration, Coroutine Environment: Coro::State.
141		410
142	AUTHOR	411	AUTHOR
143	Marc Lehmann <schmorp@schmorp.de>	412	Marc Lehmann <schmorp@schmorp.de>
144	http://home.schmorp.de/	413	http://home.schmorp.de/
145		414

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing Coro/README (file contents): Revision 1.2 by root, Sat Aug 20 01:10:22 2005 UTC vs. Revision 1.15 by root, Sun Sep 21 01:23:26 2008 UTC

Diff Legend

Comparing Coro/README (file contents):
Revision 1.2 by root, Sat Aug 20 01:10:22 2005 UTC vs.
Revision 1.15 by root, Sun Sep 21 01:23:26 2008 UTC