Coro/Coro.pm

=head1 NAME

Coro - coroutine process abstraction

=head1 SYNOPSIS

 use Coro;

 async {
    # some asynchronous thread of execution
 };

 # alternatively create an async coroutine like this:

 sub some_func : Coro {
    # some more async code
 }

 cede;

=head1 DESCRIPTION

This module collection manages coroutines. Coroutines are similar
to threads but don't run in parallel at the same time even on SMP
machines. The specific flavor of coroutine used in this module also
guarantees you that it will not switch between coroutines unless
necessary, at easily-identified points in your program, so locking and
parallel access are rarely an issue, making coroutine programming much
safer than threads programming.

(Perl, however, does not natively support real threads but instead does a
very slow and memory-intensive emulation of processes using threads. This
is a performance win on Windows machines, and a loss everywhere else).

In this module, coroutines are defined as "callchain + lexical variables +
@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
its own set of lexicals and its own set of perls most important global
variables.

=cut

package Coro;

use strict;
no warnings "uninitialized";

use Coro::State;

use base qw(Coro::State Exporter);

our $idle;    # idle handler
our $main;    # main coroutine
our $current; # current coroutine

our $VERSION = '3.7';

our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
our %EXPORT_TAGS = (
      prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
);
our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));

{
   my @async;
   my $init;

   # this way of handling attributes simply is NOT scalable ;()
   sub import {
      no strict 'refs';

      Coro->export_to_level (1, @_);

      my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
      *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
         my ($package, $ref) = (shift, shift);
         my @attrs;
         for (@_) {
            if ($_ eq "Coro") {
               push @async, $ref;
               unless ($init++) {
                  eval q{
                     sub INIT {
                        &async(pop @async) while @async;
                     }
                  };
               }
            } else {
               push @attrs, $_;
            }
         }
         return $old ? $old->($package, $ref, @attrs) : @attrs;
      };
   }

}

=over 4

=item $main

This coroutine represents the main program.

=cut

$main = new Coro;

=item $current (or as function: current)

The current coroutine (the last coroutine switched to). The initial value
is C<$main> (of course).

This variable is B<strictly> I<read-only>. It is provided for performance
reasons. If performance is not essential you are encouraged to use the
C<Coro::current> function instead.

=cut

# maybe some other module used Coro::Specific before...
$main->{specific} = $current->{specific}
   if $current;

_set_current $main;

sub current() { $current }

=item $idle

A callback that is called whenever the scheduler finds no ready coroutines
to run. The default implementation prints "FATAL: deadlock detected" and
exits, because the program has no other way to continue.

This hook is overwritten by modules such as C<Coro::Timer> and
C<Coro::Event> to wait on an external event that hopefully wake up a
coroutine so the scheduler can run it.

Please note that if your callback recursively invokes perl (e.g. for event
handlers), then it must be prepared to be called recursively.

=cut

$idle = sub {
   require Carp;
   Carp::croak ("FATAL: deadlock detected");
};

sub _cancel {
   my ($self) = @_;

   # free coroutine data and mark as destructed
   $self->_destroy
      or return;

   # call all destruction callbacks
   $_->(@{$self->{status}})
      for @{(delete $self->{destroy_cb}) || []};
}

# this coroutine is necessary because a coroutine
# cannot destroy itself.
my @destroy;
my $manager;

$manager = new Coro sub {
   $current->desc ("[coro manager]");

   while () {
      (shift @destroy)->_cancel
         while @destroy;

      &schedule;
   }
};

$manager->prio (PRIO_MAX);

# static methods. not really.

=back

=head2 STATIC METHODS

Static methods are actually functions that operate on the current coroutine only.

=over 4

=item async { ... } [@args...]

Create a new asynchronous coroutine and return it's coroutine object
(usually unused). When the sub returns the new coroutine is automatically
terminated.

Calling C<exit> in a coroutine will do the same as calling exit outside
the coroutine. Likewise, when the coroutine dies, the program will exit,
just as it would in the main program.

   # create a new coroutine that just prints its arguments
   async {
      print "@_\n";
   } 1,2,3,4;

=cut

sub async(&@) {
   my $coro = new Coro @_;
   $coro->ready;
   $coro
}

=item async_pool { ... } [@args...]

Similar to C<async>, but uses a coroutine pool, so you should not call
terminate or join (although you are allowed to), and you get a coroutine
that might have executed other code already (which can be good or bad :).

Also, the block is executed in an C<eval> context and a warning will be
issued in case of an exception instead of terminating the program, as
C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
will not work in the expected way, unless you call terminate or cancel,
which somehow defeats the purpose of pooling.

The priority will be reset to C<0> after each job, otherwise the coroutine
will be re-used "as-is".

The pool size is limited to 8 idle coroutines (this can be adjusted by
changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
required.

If you are concerned about pooled coroutines growing a lot because a
single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
terminate }> once per second or so to slowly replenish the pool.

=cut

our $POOL_SIZE = 8;
our @pool;

sub pool_handler {
   while () {
      $current->{desc} = "[async_pool]";

      eval {
         my ($cb, @arg) = @{ delete $current->{_invoke} or return };
         $cb->(@arg);
      };
      warn $@ if $@;

      last if @pool >= $POOL_SIZE;

      push @pool, $current;
      $current->{desc} = "[async_pool idle]";
      $current->save (Coro::State::SAVE_DEF);
      $current->prio (0);
      schedule;
   }
}

sub async_pool(&@) {
   # this is also inlined into the unlock_scheduler
   my $coro = (pop @pool) || new Coro \&pool_handler;;

   $coro->{_invoke} = [@_];
   $coro->ready;

   $coro
}

=item schedule

Calls the scheduler. Please note that the current coroutine will not be put
into the ready queue, so calling this function usually means you will
never be called again unless something else (e.g. an event handler) calls
ready.

The canonical way to wait on external events is this:

   {
      # remember current coroutine
      my $current = $Coro::current;

      # register a hypothetical event handler
      on_event_invoke sub {
         # wake up sleeping coroutine
         $current->ready;
         undef $current;
      };

      # call schedule until event occurred.
      # in case we are woken up for other reasons
      # (current still defined), loop.
      Coro::schedule while $current;
   }

=item cede

"Cede" to other coroutines. This function puts the current coroutine into the
ready queue and calls C<schedule>, which has the effect of giving up the
current "timeslice" to other coroutines of the same or higher priority.

Returns true if at least one coroutine switch has happened.

=item Coro::cede_notself

Works like cede, but is not exported by default and will cede to any
coroutine, regardless of priority, once.

Returns true if at least one coroutine switch has happened.

=item terminate [arg...]

Terminates the current coroutine with the given status values (see L<cancel>).

=cut

sub terminate {
   $current->cancel (@_);
}

=back

# dynamic methods

=head2 COROUTINE METHODS

These are the methods you can call on coroutine objects.

=over 4

=item new Coro \&sub [, @args...]

Create a new coroutine and return it. When the sub returns the coroutine
automatically terminates as if C<terminate> with the returned values were
called. To make the coroutine run you must first put it into the ready queue
by calling the ready method.

See C<async> for additional discussion.

=cut

sub _run_coro {
   terminate &{+shift};
}

sub new {
   my $class = shift;

   $class->SUPER::new (\&_run_coro, @_)
}

=item $success = $coroutine->ready

Put the given coroutine into the ready queue (according to it's priority)
and return true. If the coroutine is already in the ready queue, do nothing
and return false.

=item $is_ready = $coroutine->is_ready

Return wether the coroutine is currently the ready queue or not,

=item $coroutine->cancel (arg...)

Terminates the given coroutine and makes it return the given arguments as
status (default: the empty list). Never returns if the coroutine is the
current coroutine.

=cut

sub cancel {
   my $self = shift;
   $self->{status} = [@_];

   if ($current == $self) {
      push @destroy, $self;
      $manager->ready;
      &schedule while 1;
   } else {
      $self->_cancel;
   }
}

=item $coroutine->join

Wait until the coroutine terminates and return any values given to the
C<terminate> or C<cancel> functions. C<join> can be called multiple times
from multiple coroutine.

=cut

sub join {
   my $self = shift;

   unless ($self->{status}) {
      my $current = $current;

      push @{$self->{destroy_cb}}, sub {
         $current->ready;
         undef $current;
      };

      &schedule while $current;
   }

   wantarray ? @{$self->{status}} : $self->{status}[0];
}

=item $coroutine->on_destroy (\&cb)

Registers a callback that is called when this coroutine gets destroyed,
but before it is joined. The callback gets passed the terminate arguments,
if any.

=cut

sub on_destroy {
   my ($self, $cb) = @_;

   push @{ $self->{destroy_cb} }, $cb;
}

=item $oldprio = $coroutine->prio ($newprio)

Sets (or gets, if the argument is missing) the priority of the
coroutine. Higher priority coroutines get run before lower priority
coroutines. Priorities are small signed integers (currently -4 .. +3),
that you can refer to using PRIO_xxx constants (use the import tag :prio
to get then):

   PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
       3    >     1     >      0      >    -1    >    -3     >    -4

   # set priority to HIGH
   current->prio(PRIO_HIGH);

The idle coroutine ($Coro::idle) always has a lower priority than any
existing coroutine.

Changing the priority of the current coroutine will take effect immediately,
but changing the priority of coroutines in the ready queue (but not
running) will only take effect after the next schedule (of that
coroutine). This is a bug that will be fixed in some future version.

=item $newprio = $coroutine->nice ($change)

Similar to C<prio>, but subtract the given value from the priority (i.e.
higher values mean lower priority, just as in unix).

=item $olddesc = $coroutine->desc ($newdesc)

Sets (or gets in case the argument is missing) the description for this
coroutine. This is just a free-form string you can associate with a coroutine.

=cut

sub desc {
   my $old = $_[0]{desc};
   $_[0]{desc} = $_[1] if @_ > 1;
   $old;
}

=back

=head2 GLOBAL FUNCTIONS

=over 4

=item Coro::nready

Returns the number of coroutines that are currently in the ready state,
i.e. that can be switched to. The value C<0> means that the only runnable
coroutine is the currently running one, so C<cede> would have no effect,
and C<schedule> would cause a deadlock unless there is an idle handler
that wakes up some coroutines.

=item my $guard = Coro::guard { ... }

This creates and returns a guard object. Nothing happens until the object
gets destroyed, in which case the codeblock given as argument will be
executed. This is useful to free locks or other resources in case of a
runtime error or when the coroutine gets canceled, as in both cases the
guard block will be executed. The guard object supports only one method,
C<< ->cancel >>, which will keep the codeblock from being executed.

Example: set some flag and clear it again when the coroutine gets canceled
or the function returns:

   sub do_something {
      my $guard = Coro::guard { $busy = 0 };
      $busy = 1;

      # do something that requires $busy to be true
   }

=cut

sub guard(&) {
   bless \(my $cb = $_[0]), "Coro::guard"
}

sub Coro::guard::cancel {
   ${$_[0]} = sub { };
}

sub Coro::guard::DESTROY {
   ${$_[0]}->();
}


=item unblock_sub { ... }

This utility function takes a BLOCK or code reference and "unblocks" it,
returning the new coderef. This means that the new coderef will return
immediately without blocking, returning nothing, while the original code
ref will be called (with parameters) from within its own coroutine.

The reason this function exists is that many event libraries (such as the
venerable L<Event|Event> module) are not coroutine-safe (a weaker form
of thread-safety). This means you must not block within event callbacks,
otherwise you might suffer from crashes or worse.

This function allows your callbacks to block by executing them in another
coroutine where it is safe to block. One example where blocking is handy
is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
disk.

In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
creating event callbacks that want to block.

=cut

our @unblock_queue;

# we create a special coro because we want to cede,
# to reduce pressure on the coro pool (because most callbacks
# return immediately and can be reused) and because we cannot cede
# inside an event callback.
our $unblock_scheduler = async {
   $current->desc ("[unblock_sub scheduler]");
   while () {
      while (my $cb = pop @unblock_queue) {
         # this is an inlined copy of async_pool
         my $coro = (pop @pool or new Coro \&pool_handler);

         $coro->{_invoke} = $cb;
         $coro->ready;
         cede; # for short-lived callbacks, this reduces pressure on the coro pool
      }
      schedule; # sleep well
   }
};

sub unblock_sub(&) {
   my $cb = shift;

   sub {
      unshift @unblock_queue, [$cb, @_];
      $unblock_scheduler->ready;
   }
}

=back

=cut

1;

=head1 BUGS/LIMITATIONS

 - you must make very sure that no coro is still active on global
   destruction. very bad things might happen otherwise (usually segfaults).

 - this module is not thread-safe. You should only ever use this module
   from the same thread (this requirement might be loosened in the future
   to allow per-thread schedulers, but Coro::State does not yet allow
   this).

=head1 SEE ALSO

Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.

Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.

Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.

Embedding: L<Coro:MakeMaker>

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

Revision:	1.129
Committed:	Wed Sep 19 22:33:08 2007 UTC (16 years, 8 months ago) by root
Branch:	MAIN
Changes since 1.128:	+8 -6 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.8	Coro - coroutine process abstraction
4	root	1.1
5			=head1 SYNOPSIS
6
7			use Coro;
8
9	root	1.8	async {
10			# some asynchronous thread of execution
11	root	1.2	};
12
13	root	1.92	# alternatively create an async coroutine like this:
14	root	1.6
15	root	1.8	sub some_func : Coro {
16			# some more async code
17			}
18
19	root	1.22	cede;
20	root	1.2
21	root	1.1	=head1 DESCRIPTION
22
23	root	1.98	This module collection manages coroutines. Coroutines are similar
24			to threads but don't run in parallel at the same time even on SMP
25	root	1.124	machines. The specific flavor of coroutine used in this module also
26			guarantees you that it will not switch between coroutines unless
27	root	1.98	necessary, at easily-identified points in your program, so locking and
28			parallel access are rarely an issue, making coroutine programming much
29			safer than threads programming.
30
31			(Perl, however, does not natively support real threads but instead does a
32			very slow and memory-intensive emulation of processes using threads. This
33			is a performance win on Windows machines, and a loss everywhere else).
34
35			In this module, coroutines are defined as "callchain + lexical variables +
36			@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
37			its own set of lexicals and its own set of perls most important global
38			variables.
39	root	1.22
40	root	1.8	=cut
41
42			package Coro;
43
44	root	1.71	use strict;
45			no warnings "uninitialized";
46	root	1.36
47	root	1.8	use Coro::State;
48
49	root	1.83	use base qw(Coro::State Exporter);
50	pcg	1.55
51	root	1.83	our $idle; # idle handler
52	root	1.71	our $main; # main coroutine
53			our $current; # current coroutine
54	root	1.8
55	root	1.128	our $VERSION = '3.7';
56	root	1.8
57	root	1.105	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
58	root	1.71	our %EXPORT_TAGS = (
59	root	1.31	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60			);
61	root	1.97	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
62	root	1.8
63			{
64			my @async;
65	root	1.26	my $init;
66	root	1.8
67			# this way of handling attributes simply is NOT scalable ;()
68			sub import {
69	root	1.71	no strict 'refs';
70
71	root	1.93	Coro->export_to_level (1, @_);
72	root	1.71
73	root	1.8	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
74			*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
75			my ($package, $ref) = (shift, shift);
76			my @attrs;
77			for (@_) {
78			if ($_ eq "Coro") {
79			push @async, $ref;
80	root	1.26	unless ($init++) {
81			eval q{
82			sub INIT {
83			&async(pop @async) while @async;
84			}
85			};
86			}
87	root	1.8	} else {
88	root	1.17	push @attrs, $_;
89	root	1.8	}
90			}
91	root	1.17	return $old ? $old->($package, $ref, @attrs) : @attrs;
92	root	1.8	};
93			}
94
95			}
96
97	root	1.43	=over 4
98
99	root	1.8	=item $main
100	root	1.2
101	root	1.8	This coroutine represents the main program.
102	root	1.1
103			=cut
104
105	pcg	1.55	$main = new Coro;
106	root	1.8
107	root	1.19	=item $current (or as function: current)
108	root	1.1
109	root	1.83	The current coroutine (the last coroutine switched to). The initial value
110			is C<$main> (of course).
111
112			This variable is B<strictly> I<read-only>. It is provided for performance
113	root	1.124	reasons. If performance is not essential you are encouraged to use the
114	root	1.83	C<Coro::current> function instead.
115	root	1.1
116	root	1.8	=cut
117
118			# maybe some other module used Coro::Specific before...
119	root	1.93	$main->{specific} = $current->{specific}
120			if $current;
121	root	1.1
122	root	1.93	_set_current $main;
123	root	1.19
124			sub current() { $current }
125	root	1.9
126			=item $idle
127
128	root	1.83	A callback that is called whenever the scheduler finds no ready coroutines
129			to run. The default implementation prints "FATAL: deadlock detected" and
130	root	1.91	exits, because the program has no other way to continue.
131	root	1.83
132			This hook is overwritten by modules such as C<Coro::Timer> and
133	root	1.91	C<Coro::Event> to wait on an external event that hopefully wake up a
134			coroutine so the scheduler can run it.
135
136			Please note that if your callback recursively invokes perl (e.g. for event
137			handlers), then it must be prepared to be called recursively.
138	root	1.9
139			=cut
140
141	root	1.83	$idle = sub {
142	root	1.96	require Carp;
143			Carp::croak ("FATAL: deadlock detected");
144	root	1.9	};
145	root	1.8
146	root	1.103	sub _cancel {
147			my ($self) = @_;
148
149			# free coroutine data and mark as destructed
150			$self->_destroy
151			or return;
152
153			# call all destruction callbacks
154			$_->(@{$self->{status}})
155			for @{(delete $self->{destroy_cb}) \|\| []};
156			}
157
158	root	1.24	# this coroutine is necessary because a coroutine
159			# cannot destroy itself.
160			my @destroy;
161	root	1.103	my $manager;
162
163			$manager = new Coro sub {
164	root	1.129	$current->desc ("[coro manager]");
165
166	pcg	1.57	while () {
167	root	1.103	(shift @destroy)->_cancel
168			while @destroy;
169
170	root	1.24	&schedule;
171			}
172			};
173
174	root	1.103	$manager->prio (PRIO_MAX);
175
176	root	1.8	# static methods. not really.
177	root	1.43
178			=back
179	root	1.8
180			=head2 STATIC METHODS
181
182	root	1.92	Static methods are actually functions that operate on the current coroutine only.
183	root	1.8
184			=over 4
185
186	root	1.13	=item async { ... } [@args...]
187	root	1.8
188	root	1.92	Create a new asynchronous coroutine and return it's coroutine object
189			(usually unused). When the sub returns the new coroutine is automatically
190	root	1.8	terminated.
191
192	root	1.122	Calling C<exit> in a coroutine will do the same as calling exit outside
193			the coroutine. Likewise, when the coroutine dies, the program will exit,
194			just as it would in the main program.
195	root	1.79
196	root	1.13	# create a new coroutine that just prints its arguments
197			async {
198			print "@_\n";
199			} 1,2,3,4;
200
201	root	1.8	=cut
202
203	root	1.13	sub async(&@) {
204	root	1.104	my $coro = new Coro @_;
205			$coro->ready;
206			$coro
207	root	1.8	}
208	root	1.1
209	root	1.105	=item async_pool { ... } [@args...]
210
211			Similar to C<async>, but uses a coroutine pool, so you should not call
212			terminate or join (although you are allowed to), and you get a coroutine
213			that might have executed other code already (which can be good or bad :).
214
215			Also, the block is executed in an C<eval> context and a warning will be
216	root	1.108	issued in case of an exception instead of terminating the program, as
217			C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
218			will not work in the expected way, unless you call terminate or cancel,
219			which somehow defeats the purpose of pooling.
220	root	1.105
221			The priority will be reset to C<0> after each job, otherwise the coroutine
222			will be re-used "as-is".
223
224			The pool size is limited to 8 idle coroutines (this can be adjusted by
225			changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
226			required.
227
228			If you are concerned about pooled coroutines growing a lot because a
229			single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
230			terminate }> once per second or so to slowly replenish the pool.
231
232			=cut
233
234			our $POOL_SIZE = 8;
235			our @pool;
236
237			sub pool_handler {
238			while () {
239	root	1.129	$current->{desc} = "[async_pool]";
240
241	root	1.105	eval {
242	root	1.110	my ($cb, @arg) = @{ delete $current->{_invoke} or return };
243	root	1.105	$cb->(@arg);
244			};
245			warn $@ if $@;
246
247			last if @pool >= $POOL_SIZE;
248	root	1.129
249	root	1.105	push @pool, $current;
250	root	1.129	$current->{desc} = "[async_pool idle]";
251	root	1.118	$current->save (Coro::State::SAVE_DEF);
252	root	1.105	$current->prio (0);
253			schedule;
254	root	1.106	}
255			}
256	root	1.105
257			sub async_pool(&@) {
258			# this is also inlined into the unlock_scheduler
259	root	1.129	my $coro = (pop @pool) \|\| new Coro \&pool_handler;;
260	root	1.105
261			$coro->{_invoke} = [@_];
262			$coro->ready;
263
264			$coro
265			}
266
267	root	1.8	=item schedule
268	root	1.6
269	root	1.92	Calls the scheduler. Please note that the current coroutine will not be put
270	root	1.8	into the ready queue, so calling this function usually means you will
271	root	1.91	never be called again unless something else (e.g. an event handler) calls
272			ready.
273
274			The canonical way to wait on external events is this:
275
276			{
277	root	1.92	# remember current coroutine
278	root	1.91	my $current = $Coro::current;
279
280			# register a hypothetical event handler
281			on_event_invoke sub {
282			# wake up sleeping coroutine
283			$current->ready;
284			undef $current;
285			};
286
287	root	1.124	# call schedule until event occurred.
288	root	1.91	# in case we are woken up for other reasons
289			# (current still defined), loop.
290			Coro::schedule while $current;
291			}
292	root	1.1
293	root	1.22	=item cede
294	root	1.1
295	root	1.92	"Cede" to other coroutines. This function puts the current coroutine into the
296	root	1.22	ready queue and calls C<schedule>, which has the effect of giving up the
297			current "timeslice" to other coroutines of the same or higher priority.
298	root	1.7
299	root	1.107	Returns true if at least one coroutine switch has happened.
300
301	root	1.102	=item Coro::cede_notself
302
303			Works like cede, but is not exported by default and will cede to any
304			coroutine, regardless of priority, once.
305
306	root	1.107	Returns true if at least one coroutine switch has happened.
307
308	root	1.40	=item terminate [arg...]
309	root	1.7
310	root	1.92	Terminates the current coroutine with the given status values (see L<cancel>).
311	root	1.13
312	root	1.1	=cut
313
314	root	1.8	sub terminate {
315	pcg	1.59	$current->cancel (@_);
316	root	1.1	}
317	root	1.6
318	root	1.8	=back
319
320			# dynamic methods
321
322	root	1.92	=head2 COROUTINE METHODS
323	root	1.8
324	root	1.92	These are the methods you can call on coroutine objects.
325	root	1.6
326	root	1.8	=over 4
327
328	root	1.13	=item new Coro \&sub [, @args...]
329	root	1.8
330	root	1.92	Create a new coroutine and return it. When the sub returns the coroutine
331	root	1.40	automatically terminates as if C<terminate> with the returned values were
332	root	1.92	called. To make the coroutine run you must first put it into the ready queue
333	root	1.41	by calling the ready method.
334	root	1.13
335	root	1.121	See C<async> for additional discussion.
336	root	1.89
337	root	1.6	=cut
338
339	root	1.94	sub _run_coro {
340	root	1.13	terminate &{+shift};
341			}
342
343	root	1.8	sub new {
344			my $class = shift;
345	root	1.83
346	root	1.94	$class->SUPER::new (\&_run_coro, @_)
347	root	1.8	}
348	root	1.6
349	root	1.92	=item $success = $coroutine->ready
350	root	1.1
351	root	1.92	Put the given coroutine into the ready queue (according to it's priority)
352			and return true. If the coroutine is already in the ready queue, do nothing
353	root	1.90	and return false.
354	root	1.1
355	root	1.92	=item $is_ready = $coroutine->is_ready
356	root	1.90
357	root	1.92	Return wether the coroutine is currently the ready queue or not,
358	root	1.28
359	root	1.92	=item $coroutine->cancel (arg...)
360	root	1.28
361	root	1.92	Terminates the given coroutine and makes it return the given arguments as
362	root	1.103	status (default: the empty list). Never returns if the coroutine is the
363			current coroutine.
364	root	1.28
365			=cut
366
367			sub cancel {
368	pcg	1.59	my $self = shift;
369			$self->{status} = [@_];
370	root	1.103
371			if ($current == $self) {
372			push @destroy, $self;
373			$manager->ready;
374			&schedule while 1;
375			} else {
376			$self->_cancel;
377			}
378	root	1.40	}
379
380	root	1.92	=item $coroutine->join
381	root	1.40
382			Wait until the coroutine terminates and return any values given to the
383	pcg	1.59	C<terminate> or C<cancel> functions. C<join> can be called multiple times
384	root	1.92	from multiple coroutine.
385	root	1.40
386			=cut
387
388			sub join {
389			my $self = shift;
390	root	1.103
391	root	1.40	unless ($self->{status}) {
392	root	1.103	my $current = $current;
393
394			push @{$self->{destroy_cb}}, sub {
395			$current->ready;
396			undef $current;
397			};
398
399			&schedule while $current;
400	root	1.40	}
401	root	1.103
402	root	1.40	wantarray ? @{$self->{status}} : $self->{status}[0];
403	root	1.31	}
404
405	root	1.101	=item $coroutine->on_destroy (\&cb)
406
407			Registers a callback that is called when this coroutine gets destroyed,
408			but before it is joined. The callback gets passed the terminate arguments,
409			if any.
410
411			=cut
412
413			sub on_destroy {
414			my ($self, $cb) = @_;
415
416			push @{ $self->{destroy_cb} }, $cb;
417			}
418
419	root	1.92	=item $oldprio = $coroutine->prio ($newprio)
420	root	1.31
421	root	1.41	Sets (or gets, if the argument is missing) the priority of the
422	root	1.92	coroutine. Higher priority coroutines get run before lower priority
423			coroutines. Priorities are small signed integers (currently -4 .. +3),
424	root	1.41	that you can refer to using PRIO_xxx constants (use the import tag :prio
425			to get then):
426	root	1.31
427			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
428			3 > 1 > 0 > -1 > -3 > -4
429
430			# set priority to HIGH
431			current->prio(PRIO_HIGH);
432
433			The idle coroutine ($Coro::idle) always has a lower priority than any
434			existing coroutine.
435
436	root	1.92	Changing the priority of the current coroutine will take effect immediately,
437			but changing the priority of coroutines in the ready queue (but not
438	root	1.31	running) will only take effect after the next schedule (of that
439	root	1.92	coroutine). This is a bug that will be fixed in some future version.
440	root	1.31
441	root	1.92	=item $newprio = $coroutine->nice ($change)
442	root	1.31
443			Similar to C<prio>, but subtract the given value from the priority (i.e.
444			higher values mean lower priority, just as in unix).
445
446	root	1.92	=item $olddesc = $coroutine->desc ($newdesc)
447	root	1.41
448			Sets (or gets in case the argument is missing) the description for this
449	root	1.92	coroutine. This is just a free-form string you can associate with a coroutine.
450	root	1.41
451			=cut
452
453			sub desc {
454			my $old = $_[0]{desc};
455			$_[0]{desc} = $_[1] if @_ > 1;
456			$old;
457	root	1.8	}
458	root	1.1
459	root	1.8	=back
460	root	1.2
461	root	1.97	=head2 GLOBAL FUNCTIONS
462	root	1.92
463			=over 4
464
465	root	1.97	=item Coro::nready
466
467			Returns the number of coroutines that are currently in the ready state,
468	root	1.124	i.e. that can be switched to. The value C<0> means that the only runnable
469	root	1.97	coroutine is the currently running one, so C<cede> would have no effect,
470			and C<schedule> would cause a deadlock unless there is an idle handler
471			that wakes up some coroutines.
472
473	root	1.103	=item my $guard = Coro::guard { ... }
474
475	root	1.119	This creates and returns a guard object. Nothing happens until the object
476	root	1.103	gets destroyed, in which case the codeblock given as argument will be
477			executed. This is useful to free locks or other resources in case of a
478			runtime error or when the coroutine gets canceled, as in both cases the
479			guard block will be executed. The guard object supports only one method,
480			C<< ->cancel >>, which will keep the codeblock from being executed.
481
482			Example: set some flag and clear it again when the coroutine gets canceled
483			or the function returns:
484
485			sub do_something {
486			my $guard = Coro::guard { $busy = 0 };
487			$busy = 1;
488
489			# do something that requires $busy to be true
490			}
491
492			=cut
493
494			sub guard(&) {
495			bless \(my $cb = $_[0]), "Coro::guard"
496			}
497
498			sub Coro::guard::cancel {
499			${$_[0]} = sub { };
500			}
501
502			sub Coro::guard::DESTROY {
503			${$_[0]}->();
504			}
505
506
507	root	1.92	=item unblock_sub { ... }
508
509			This utility function takes a BLOCK or code reference and "unblocks" it,
510			returning the new coderef. This means that the new coderef will return
511			immediately without blocking, returning nothing, while the original code
512			ref will be called (with parameters) from within its own coroutine.
513
514	root	1.124	The reason this function exists is that many event libraries (such as the
515	root	1.92	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
516			of thread-safety). This means you must not block within event callbacks,
517			otherwise you might suffer from crashes or worse.
518
519			This function allows your callbacks to block by executing them in another
520			coroutine where it is safe to block. One example where blocking is handy
521			is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
522			disk.
523
524			In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
525			creating event callbacks that want to block.
526
527			=cut
528
529			our @unblock_queue;
530
531	root	1.105	# we create a special coro because we want to cede,
532			# to reduce pressure on the coro pool (because most callbacks
533			# return immediately and can be reused) and because we cannot cede
534			# inside an event callback.
535	root	1.92	our $unblock_scheduler = async {
536	root	1.129	$current->desc ("[unblock_sub scheduler]");
537	root	1.92	while () {
538			while (my $cb = pop @unblock_queue) {
539	root	1.105	# this is an inlined copy of async_pool
540			my $coro = (pop @pool or new Coro \&pool_handler);
541
542			$coro->{_invoke} = $cb;
543			$coro->ready;
544			cede; # for short-lived callbacks, this reduces pressure on the coro pool
545	root	1.92	}
546	root	1.105	schedule; # sleep well
547	root	1.92	}
548			};
549
550			sub unblock_sub(&) {
551			my $cb = shift;
552
553			sub {
554	root	1.105	unshift @unblock_queue, [$cb, @_];
555	root	1.92	$unblock_scheduler->ready;
556			}
557			}
558
559			=back
560
561	root	1.8	=cut
562	root	1.2
563	root	1.8	1;
564	root	1.14
565	root	1.17	=head1 BUGS/LIMITATIONS
566	root	1.14
567	root	1.52	- you must make very sure that no coro is still active on global
568	root	1.53	destruction. very bad things might happen otherwise (usually segfaults).
569	root	1.52
570			- this module is not thread-safe. You should only ever use this module
571	root	1.124	from the same thread (this requirement might be loosened in the future
572	root	1.52	to allow per-thread schedulers, but Coro::State does not yet allow
573			this).
574	root	1.9
575			=head1 SEE ALSO
576
577	root	1.67	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
578
579			Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
580
581			Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
582
583			Embedding: L<Coro:MakeMaker>
584	root	1.1
585			=head1 AUTHOR
586
587	root	1.66	Marc Lehmann <schmorp@schmorp.de>
588	root	1.64	http://home.schmorp.de/
589	root	1.1
590			=cut
591