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Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs.
Revision 1.56 by pcg, Sat Nov 15 03:53:10 2003 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+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
33more useful process abstraction including scheduling. 28callchain, it's own set of lexicals and it's own set of perl's most
29important global variables.
30
31=cut
32
33package Coro;
34
35BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") }
36
37use Coro::State;
38
39use vars qw($idle $main $current);
40
41use base Exporter;
42
43$VERSION = "0.9";
44
45@EXPORT = qw(async cede schedule terminate current);
46%EXPORT_TAGS = (
47 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48);
49@EXPORT_OK = @{$EXPORT_TAGS{prio}};
50
51{
52 my @async;
53 my $init;
54
55 # this way of handling attributes simply is NOT scalable ;()
56 sub import {
57 Coro->export_to_level(1, @_);
58 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
59 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
60 my ($package, $ref) = (shift, shift);
61 my @attrs;
62 for (@_) {
63 if ($_ eq "Coro") {
64 push @async, $ref;
65 unless ($init++) {
66 eval q{
67 sub INIT {
68 &async(pop @async) while @async;
69 }
70 };
71 }
72 } else {
73 push @attrs, $_;
74 }
75 }
76 return $old ? $old->($package, $ref, @attrs) : @attrs;
77 };
78 }
79
80}
34 81
35=over 4 82=over 4
36 83
37=cut 84=item $main
38 85
39package Coro; 86This coroutine represents the main program.
40 87
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 88=cut
89
90$main = new Coro;
91
92=item $current (or as function: current)
93
94The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
95
96=cut
97
98# maybe some other module used Coro::Specific before...
99if ($current) {
100 $main->{specific} = $current->{specific};
101}
102
103$current = $main;
104
105sub current() { $current }
106
107=item $idle
108
109The coroutine to switch to when no other coroutine is running. The default
110implementation prints "FATAL: deadlock detected" and exits.
111
112=cut
113
114# should be done using priorities :(
115$idle = new Coro sub {
116 print STDERR "FATAL: deadlock detected\n";
117 exit(51);
118};
119
120# this coroutine is necessary because a coroutine
121# cannot destroy itself.
122my @destroy;
123my $manager;
124$manager = new Coro sub {
125 while() {
126 # by overwriting the state object with the manager we destroy it
127 # while still being able to schedule this coroutine (in case it has
128 # been readied multiple times. this is harmless since the manager
129 # can be called as many times as neccessary and will always
130 # remove itself from the runqueue
131 while (@destroy) {
132 my $coro = pop @destroy;
133 $coro->{status} ||= [];
134 $_->ready for @{delete $coro->{join} || []};
135 $coro->{_coro_state} = $manager->{_coro_state};
136 }
137 &schedule;
138 }
139};
140
141# static methods. not really.
142
143=back
144
145=head2 STATIC METHODS
146
147Static methods are actually functions that operate on the current process only.
148
149=over 4
150
151=item async { ... } [@args...]
152
153Create a new asynchronous process and return it's process object
154(usually unused). When the sub returns the new process is automatically
155terminated.
156
157 # create a new coroutine that just prints its arguments
158 async {
159 print "@_\n";
160 } 1,2,3,4;
161
162The coderef you submit MUST NOT be a closure that refers to variables
163in an outer scope. This does NOT work. Pass arguments into it instead.
164
165=cut
166
167sub async(&@) {
168 my $pid = new Coro @_;
169 $manager->ready; # this ensures that the stack is cloned from the manager
170 $pid->ready;
171 $pid;
172}
173
174=item schedule
175
176Calls the scheduler. Please note that the current process will not be put
177into the ready queue, so calling this function usually means you will
178never be called again.
179
180=cut
181
182=item cede
183
184"Cede" to other processes. This function puts the current process into the
185ready queue and calls C<schedule>, which has the effect of giving up the
186current "timeslice" to other coroutines of the same or higher priority.
187
188=cut
189
190=item terminate [arg...]
191
192Terminates the current process.
193
194Future versions of this function will allow result arguments.
195
196=cut
197
198sub terminate {
199 $current->{status} = [@_];
200 $current->cancel;
201 &schedule;
202 die; # NORETURN
203}
204
205=back
206
207# dynamic methods
208
209=head2 PROCESS METHODS
210
211These are the methods you can call on process objects.
212
213=over 4
214
215=item new Coro \&sub [, @args...]
216
217Create a new process and return it. When the sub returns the process
218automatically terminates as if C<terminate> with the returned values were
219called. To make the process run you must first put it into the ready queue
220by calling the ready method.
221
222=cut
223
224sub _newcoro {
225 terminate &{+shift};
226}
59 227
60sub new { 228sub new {
61 my $class = $_[0]; 229 my $class = shift;
62 my $proc = $_[1] || sub { die "tried to transfer to an empty coroutine" }; 230 bless {
63 bless _newprocess { 231 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
64 do {
65 eval { &$proc };
66 if ($@) {
67 $error_msg = $@;
68 $error_coro = _newprocess { };
69 &transfer($error_coro, $error);
70 }
71 } while (1);
72 }, $class; 232 }, $class;
73} 233}
74 234
75=item $prev->transfer($next) 235=item $process->ready
76 236
77Save the state of the current subroutine in C<$prev> and switch to the 237Put the given process into the ready queue.
78coroutine saved in C<$next>.
79 238
80The "state" of a subroutine only ever includes scope, i.e. lexical 239=cut
81variables and the current execution state. It does not save/restore any
82global variables such as C<$_> or C<$@> or any other special or non
83special variables. So remember that every function call that might call
84C<transfer> (such as C<Coro::Channel::put>) might clobber any global
85and/or special variables. Yes, this is by design ;) You cna always create
86your own process abstraction model that saves these variables.
87 240
88The easiest way to do this is to create your own scheduling primitive like this: 241=item $process->cancel
89 242
90 sub schedule { 243Like C<terminate>, but terminates the specified process instead.
91 local ($_, $@, ...); 244
92 $old->transfer($new); 245=cut
246
247sub cancel {
248 push @destroy, $_[0];
249 $manager->ready;
250 &schedule if $current == $_[0];
251}
252
253=item $process->join
254
255Wait until the coroutine terminates and return any values given to the
256C<terminate> function. C<join> can be called multiple times from multiple
257processes.
258
259=cut
260
261sub join {
262 my $self = shift;
263 unless ($self->{status}) {
264 push @{$self->{join}}, $current;
265 &schedule;
93 } 266 }
94 267 wantarray ? @{$self->{status}} : $self->{status}[0];
95=cut
96
97# I call the _transfer function from a perl function
98# because that way perl saves all important things on
99# the stack. Actually, I'd do it from within XS, but
100# I couldn't get it to work.
101sub transfer {
102 _transfer($_[0], $_[1]);
103} 268}
104 269
105=item $error, $error_msg, $error_coro 270=item $oldprio = $process->prio($newprio)
106 271
107This coroutine will be called on fatal errors. C<$error_msg> and 272Sets (or gets, if the argument is missing) the priority of the
108C<$error_coro> return the error message and the error-causing coroutine 273process. Higher priority processes get run before lower priority
109(NOT an object) respectively. This API might change. 274processes. Priorities are small signed integers (currently -4 .. +3),
275that you can refer to using PRIO_xxx constants (use the import tag :prio
276to get then):
110 277
111=cut 278 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
279 3 > 1 > 0 > -1 > -3 > -4
112 280
113$error_msg = 281 # set priority to HIGH
114$error_coro = undef; 282 current->prio(PRIO_HIGH);
115 283
116$error = _newprocess { 284The idle coroutine ($Coro::idle) always has a lower priority than any
117 print STDERR "FATAL: $error_msg\nprogram aborted\n"; 285existing coroutine.
118 exit 50; 286
119}; 287Changing the priority of the current process will take effect immediately,
288but changing the priority of processes in the ready queue (but not
289running) will only take effect after the next schedule (of that
290process). This is a bug that will be fixed in some future version.
291
292=cut
293
294sub prio {
295 my $old = $_[0]{prio};
296 $_[0]{prio} = $_[1] if @_ > 1;
297 $old;
298}
299
300=item $newprio = $process->nice($change)
301
302Similar to C<prio>, but subtract the given value from the priority (i.e.
303higher values mean lower priority, just as in unix).
304
305=cut
306
307sub nice {
308 $_[0]{prio} -= $_[1];
309}
310
311=item $olddesc = $process->desc($newdesc)
312
313Sets (or gets in case the argument is missing) the description for this
314process. This is just a free-form string you can associate with a process.
315
316=cut
317
318sub desc {
319 my $old = $_[0]{desc};
320 $_[0]{desc} = $_[1] if @_ > 1;
321 $old;
322}
323
324=back
325
326=cut
120 327
1211; 3281;
122 329
123=back 330=head1 BUGS/LIMITATIONS
124 331
125=head1 BUGS 332 - you must make very sure that no coro is still active on global
333 destruction. very bad things might happen otherwise (usually segfaults).
126 334
127This module has not yet been extensively tested. 335 - this module is not thread-safe. You should only ever use this module
336 from the same thread (this requirement might be losened in the future
337 to allow per-thread schedulers, but Coro::State does not yet allow
338 this).
128 339
129=head1 SEE ALSO 340=head1 SEE ALSO
130 341
131L<Coro::Process>, L<Coro::Signal>. 342L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
343L<Coro::Signal>, L<Coro::State>, L<Coro::Timer>, L<Coro::Event>,
344L<Coro::L<Coro::RWLock>, Handle>, L<Coro::Socket>.
132 345
133=head1 AUTHOR 346=head1 AUTHOR
134 347
135 Marc Lehmann <pcg@goof.com> 348 Marc Lehmann <pcg@goof.com>
136 http://www.goof.com/pcg/marc/ 349 http://www.goof.com/pcg/marc/

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