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Revision 1.6 by root, Tue Jul 10 21:19:47 2001 UTC vs.
Revision 1.88 by root, Sun Nov 26 02:54:55 2006 UTC

1=head1 NAME 1=head1 NAME
2 2
3Coro - create and manage simple coroutines 3Coro - coroutine process abstraction
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use Coro; 7 use Coro;
8 8
9 $new = new Coro sub { 9 async {
10 print "in coroutine, switching back\n"; 10 # some asynchronous thread of execution
11 $new->transfer($main);
12 print "in coroutine again, switching back\n";
13 $new->transfer($main);
14 }; 11 };
15 12
16 $main = new Coro; 13 # alternatively create an async process like this:
17 14
18 print "in main, switching to coroutine\n"; 15 sub some_func : Coro {
19 $main->transfer($new); 16 # some more async code
20 print "back in main, switch to coroutine again\n"; 17 }
21 $main->transfer($new); 18
22 print "back in main\n"; 19 cede;
23 20
24=head1 DESCRIPTION 21=head1 DESCRIPTION
25 22
26This module implements coroutines. Coroutines, similar to continuations, 23This module collection manages coroutines. Coroutines are similar to
27allow you to run more than one "thread of execution" in parallel. Unlike 24threads but don't run in parallel.
28threads this, only voluntary switching is used so locking problems are
29greatly reduced.
30 25
31Although this is the "main" module of the Coro family it provides only 26In this module, coroutines are defined as "callchain + lexical variables
32low-level functionality. See L<Coro::Process> and related modules for a 27+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
33more useful process abstraction including scheduling. 28callchain, it's own set of lexicals and it's own set of perl's most
29important global variables.
30
31=cut
32
33package Coro;
34
35use strict;
36no warnings "uninitialized";
37
38use Coro::State;
39
40use base qw(Coro::State Exporter);
41
42our $idle; # idle handler
43our $main; # main coroutine
44our $current; # current coroutine
45
46our $VERSION = '3.0';
47
48our @EXPORT = qw(async cede schedule terminate current);
49our %EXPORT_TAGS = (
50 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51);
52our @EXPORT_OK = @{$EXPORT_TAGS{prio}};
53
54{
55 my @async;
56 my $init;
57
58 # this way of handling attributes simply is NOT scalable ;()
59 sub import {
60 no strict 'refs';
61
62 Coro->export_to_level(1, @_);
63
64 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
65 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
66 my ($package, $ref) = (shift, shift);
67 my @attrs;
68 for (@_) {
69 if ($_ eq "Coro") {
70 push @async, $ref;
71 unless ($init++) {
72 eval q{
73 sub INIT {
74 &async(pop @async) while @async;
75 }
76 };
77 }
78 } else {
79 push @attrs, $_;
80 }
81 }
82 return $old ? $old->($package, $ref, @attrs) : @attrs;
83 };
84 }
85
86}
34 87
35=over 4 88=over 4
36 89
37=cut 90=item $main
38 91
39package Coro; 92This coroutine represents the main program.
40 93
41BEGIN {
42 $VERSION = 0.03;
43
44 require XSLoader;
45 XSLoader::load Coro, $VERSION;
46}
47
48=item $coro = new [$coderef [, @args]]
49
50Create a new coroutine and return it. The first C<transfer> call to this
51coroutine will start execution at the given coderef. If, the subroutine
52returns it will be executed again.
53
54If the coderef is omitted this function will create a new "empty"
55coroutine, i.e. a coroutine that cannot be transfered to but can be used
56to save the current coroutine in.
57
58=cut 94=cut
95
96$main = new Coro;
97
98=item $current (or as function: current)
99
100The current coroutine (the last coroutine switched to). The initial value
101is C<$main> (of course).
102
103This variable is B<strictly> I<read-only>. It is provided for performance
104reasons. If performance is not essentiel you are encouraged to use the
105C<Coro::current> function instead.
106
107=cut
108
109# maybe some other module used Coro::Specific before...
110if ($current) {
111 $main->{specific} = $current->{specific};
112}
113
114$current = $main;
115
116sub current() { $current }
117
118=item $idle
119
120A callback that is called whenever the scheduler finds no ready coroutines
121to run. The default implementation prints "FATAL: deadlock detected" and
122exits.
123
124This hook is overwritten by modules such as C<Coro::Timer> and
125C<Coro::Event> to wait on an external event that hopefully wakes up some
126coroutine.
127
128=cut
129
130$idle = sub {
131 print STDERR "FATAL: deadlock detected\n";
132 exit (51);
133};
134
135# this coroutine is necessary because a coroutine
136# cannot destroy itself.
137my @destroy;
138my $manager; $manager = new Coro sub {
139 while () {
140 # by overwriting the state object with the manager we destroy it
141 # while still being able to schedule this coroutine (in case it has
142 # been readied multiple times. this is harmless since the manager
143 # can be called as many times as neccessary and will always
144 # remove itself from the runqueue
145 while (@destroy) {
146 my $coro = pop @destroy;
147 $coro->{status} ||= [];
148 $_->ready for @{delete $coro->{join} || []};
149
150 # the next line destroys the coro state, but keeps the
151 # process itself intact (we basically make it a zombie
152 # process that always runs the manager thread, so it's possible
153 # to transfer() to this process).
154 $coro->_clone_state_from ($manager);
155 }
156 &schedule;
157 }
158};
159
160# static methods. not really.
161
162=back
163
164=head2 STATIC METHODS
165
166Static methods are actually functions that operate on the current process only.
167
168=over 4
169
170=item async { ... } [@args...]
171
172Create a new asynchronous process and return it's process object
173(usually unused). When the sub returns the new process is automatically
174terminated.
175
176When the coroutine dies, the program will exit, just as in the main
177program.
178
179 # create a new coroutine that just prints its arguments
180 async {
181 print "@_\n";
182 } 1,2,3,4;
183
184=cut
185
186sub async(&@) {
187 my $pid = new Coro @_;
188 $pid->ready;
189 $pid
190}
191
192=item schedule
193
194Calls the scheduler. Please note that the current process will not be put
195into the ready queue, so calling this function usually means you will
196never be called again.
197
198=cut
199
200=item cede
201
202"Cede" to other processes. This function puts the current process into the
203ready queue and calls C<schedule>, which has the effect of giving up the
204current "timeslice" to other coroutines of the same or higher priority.
205
206=cut
207
208=item terminate [arg...]
209
210Terminates the current process with the given status values (see L<cancel>).
211
212=cut
213
214sub terminate {
215 $current->cancel (@_);
216}
217
218=back
219
220# dynamic methods
221
222=head2 PROCESS METHODS
223
224These are the methods you can call on process objects.
225
226=over 4
227
228=item new Coro \&sub [, @args...]
229
230Create a new process and return it. When the sub returns the process
231automatically terminates as if C<terminate> with the returned values were
232called. To make the process run you must first put it into the ready queue
233by calling the ready method.
234
235=cut
236
237sub _new_coro {
238 terminate &{+shift};
239}
59 240
60sub new { 241sub new {
61 my $class = $_[0]; 242 my $class = shift;
62 my $proc = $_[1] || sub { die "tried to transfer to an empty coroutine" };
63 bless _newprocess {
64 do {
65 eval { &$proc };
66 if ($@) {
67 $error_msg = $@;
68 $error_coro = _newprocess { };
69 &transfer($error_coro, $error);
70 }
71 } while (1);
72 }, $class;
73}
74 243
75=item $prev->transfer($next) 244 $class->SUPER::new (\&_new_coro, @_)
76
77Save the state of the current subroutine in $prev and switch to the
78coroutine saved in $next.
79
80=cut
81
82# I call the _transfer function from a perl function
83# because that way perl saves all important things on
84# the stack.
85sub transfer {
86 _transfer($_[0], $_[1]);
87} 245}
88 246
89=item $error, $error_msg, $error_coro 247=item $process->ready
90 248
91This coroutine will be called on fatal errors. C<$error_msg> and 249Put the given process into the ready queue.
92C<$error_coro> return the error message and the error-causing coroutine
93(NOT an object) respectively. This API might change.
94 250
95=cut 251=cut
96 252
97$error_msg = 253=item $process->cancel (arg...)
98$error_coro = undef;
99 254
100$error = _newprocess { 255Terminates the given process and makes it return the given arguments as
101 print STDERR "FATAL: $error_msg\nprogram aborted\n"; 256status (default: the empty list).
102 exit 50; 257
103}; 258=cut
259
260sub cancel {
261 my $self = shift;
262 $self->{status} = [@_];
263 push @destroy, $self;
264 $manager->ready;
265 &schedule if $current == $self;
266}
267
268=item $process->join
269
270Wait until the coroutine terminates and return any values given to the
271C<terminate> or C<cancel> functions. C<join> can be called multiple times
272from multiple processes.
273
274=cut
275
276sub join {
277 my $self = shift;
278 unless ($self->{status}) {
279 push @{$self->{join}}, $current;
280 &schedule;
281 }
282 wantarray ? @{$self->{status}} : $self->{status}[0];
283}
284
285=item $oldprio = $process->prio ($newprio)
286
287Sets (or gets, if the argument is missing) the priority of the
288process. Higher priority processes get run before lower priority
289processes. Priorities are small signed integers (currently -4 .. +3),
290that you can refer to using PRIO_xxx constants (use the import tag :prio
291to get then):
292
293 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
294 3 > 1 > 0 > -1 > -3 > -4
295
296 # set priority to HIGH
297 current->prio(PRIO_HIGH);
298
299The idle coroutine ($Coro::idle) always has a lower priority than any
300existing coroutine.
301
302Changing the priority of the current process will take effect immediately,
303but changing the priority of processes in the ready queue (but not
304running) will only take effect after the next schedule (of that
305process). This is a bug that will be fixed in some future version.
306
307=item $newprio = $process->nice ($change)
308
309Similar to C<prio>, but subtract the given value from the priority (i.e.
310higher values mean lower priority, just as in unix).
311
312=item $olddesc = $process->desc ($newdesc)
313
314Sets (or gets in case the argument is missing) the description for this
315process. This is just a free-form string you can associate with a process.
316
317=cut
318
319sub desc {
320 my $old = $_[0]{desc};
321 $_[0]{desc} = $_[1] if @_ > 1;
322 $old;
323}
324
325=back
326
327=cut
104 328
1051; 3291;
106 330
107=back 331=head1 BUGS/LIMITATIONS
108 332
109=head1 BUGS 333 - you must make very sure that no coro is still active on global
334 destruction. very bad things might happen otherwise (usually segfaults).
110 335
111This module has not yet been extensively tested. 336 - this module is not thread-safe. You should only ever use this module
337 from the same thread (this requirement might be losened in the future
338 to allow per-thread schedulers, but Coro::State does not yet allow
339 this).
112 340
113=head1 SEE ALSO 341=head1 SEE ALSO
114 342
115L<Coro::Process>, L<Coro::Signal>. 343Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
344
345Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
346
347Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
348
349Embedding: L<Coro:MakeMaker>
116 350
117=head1 AUTHOR 351=head1 AUTHOR
118 352
119 Marc Lehmann <pcg@goof.com> 353 Marc Lehmann <schmorp@schmorp.de>
120 http://www.goof.com/pcg/marc/ 354 http://home.schmorp.de/
121 355
122=cut 356=cut
123 357

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