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Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs.
Revision 1.41 by root, Tue Nov 6 20:34:09 2001 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 26This module is still experimental, see the BUGS section below.
32low-level functionality. See L<Coro::Process> and related modules for a 27
33more useful process abstraction including scheduling. 28In this module, coroutines are defined as "callchain + lexical variables
29+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
30callchain, it's own set of lexicals and it's own set of perl's most
31important global variables.
32
33=cut
34
35package Coro;
36
37no warnings qw(uninitialized);
38
39use Coro::State;
40
41use base Exporter;
42
43$VERSION = 0.52;
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}
81
82=item $main
83
84This coroutine represents the main program.
85
86=cut
87
88our $main = new Coro;
89
90=item $current (or as function: current)
91
92The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
93
94=cut
95
96# maybe some other module used Coro::Specific before...
97if ($current) {
98 $main->{specific} = $current->{specific};
99}
100
101our $current = $main;
102
103sub current() { $current }
104
105=item $idle
106
107The coroutine to switch to when no other coroutine is running. The default
108implementation prints "FATAL: deadlock detected" and exits.
109
110=cut
111
112# should be done using priorities :(
113our $idle = new Coro sub {
114 print STDERR "FATAL: deadlock detected\n";
115 exit(51);
116};
117
118# this coroutine is necessary because a coroutine
119# cannot destroy itself.
120my @destroy;
121my $manager;
122$manager = new Coro sub {
123 while() {
124 # by overwriting the state object with the manager we destroy it
125 # while still being able to schedule this coroutine (in case it has
126 # been readied multiple times. this is harmless since the manager
127 # can be called as many times as neccessary and will always
128 # remove itself from the runqueue
129 while (@destroy) {
130 my $coro = pop @destroy;
131 $coro->{status} ||= [];
132 $_->ready for @{delete $coro->{join} || []};
133 $coro->{_coro_state} = $manager->{_coro_state};
134 }
135 &schedule;
136 }
137};
138
139# static methods. not really.
140
141=head2 STATIC METHODS
142
143Static methods are actually functions that operate on the current process only.
34 144
35=over 4 145=over 4
36 146
37=cut 147=item async { ... } [@args...]
38 148
39package Coro; 149Create a new asynchronous process and return it's process object
150(usually unused). When the sub returns the new process is automatically
151terminated.
40 152
41BEGIN { 153 # create a new coroutine that just prints its arguments
42 $VERSION = 0.03; 154 async {
155 print "@_\n";
156 } 1,2,3,4;
43 157
44 require XSLoader; 158The coderef you submit MUST NOT be a closure that refers to variables
45 XSLoader::load Coro, $VERSION; 159in an outer scope. This does NOT work. Pass arguments into it instead.
46}
47 160
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 161=cut
162
163sub async(&@) {
164 my $pid = new Coro @_;
165 $manager->ready; # this ensures that the stack is cloned from the manager
166 $pid->ready;
167 $pid;
168}
169
170=item schedule
171
172Calls the scheduler. Please note that the current process will not be put
173into the ready queue, so calling this function usually means you will
174never be called again.
175
176=cut
177
178=item cede
179
180"Cede" to other processes. This function puts the current process into the
181ready queue and calls C<schedule>, which has the effect of giving up the
182current "timeslice" to other coroutines of the same or higher priority.
183
184=cut
185
186=item terminate [arg...]
187
188Terminates the current process.
189
190Future versions of this function will allow result arguments.
191
192=cut
193
194sub terminate {
195 $current->{status} = [@_];
196 $current->cancel;
197 &schedule;
198 die; # NORETURN
199}
200
201=back
202
203# dynamic methods
204
205=head2 PROCESS METHODS
206
207These are the methods you can call on process objects.
208
209=over 4
210
211=item new Coro \&sub [, @args...]
212
213Create a new process and return it. When the sub returns the process
214automatically terminates as if C<terminate> with the returned values were
215called. To make the process run you must first put it into the ready queue
216by calling the ready method.
217
218=cut
219
220sub _newcoro {
221 terminate &{+shift};
222}
59 223
60sub new { 224sub new {
61 my $class = $_[0]; 225 my $class = shift;
62 my $proc = $_[1] || sub { die "tried to transfer to an empty coroutine" }; 226 bless {
63 bless _newprocess { 227 _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; 228 }, $class;
73} 229}
74 230
75=item $prev->transfer($next) 231=item $process->ready
76 232
77Save the state of the current subroutine in C<$prev> and switch to the 233Put the given process into the ready queue.
78coroutine saved in C<$next>.
79 234
80The "state" of a subroutine only ever includes scope, i.e. lexical 235=cut
81variables and the current execution state. It does not save/restore any
82global variables such as C<$_> 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.
87 236
88The easiest way to do this is to create your own scheduling primitive like this: 237=item $process->cancel
89 238
90 sub schedule { 239Like C<terminate>, but terminates the specified process instead.
91 local ($_, $@, ...); 240
92 $old->transfer($new); 241=cut
242
243sub cancel {
244 push @destroy, $_[0];
245 $manager->ready;
246 &schedule if $current == $_[0];
247}
248
249=item $process->join
250
251Wait until the coroutine terminates and return any values given to the
252C<terminate> function. C<join> can be called multiple times from multiple
253processes.
254
255=cut
256
257sub join {
258 my $self = shift;
259 unless ($self->{status}) {
260 push @{$self->{join}}, $current;
261 &schedule;
93 } 262 }
94 263 wantarray ? @{$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} 264}
104 265
105=item $error, $error_msg, $error_coro 266=item $oldprio = $process->prio($newprio)
106 267
107This coroutine will be called on fatal errors. C<$error_msg> and 268Sets (or gets, if the argument is missing) the priority of the
108C<$error_coro> return the error message and the error-causing coroutine 269process. Higher priority processes get run before lower priority
109(NOT an object) respectively. This API might change. 270processes. Priorities are smalled signed integer (currently -4 .. +3),
271that you can refer to using PRIO_xxx constants (use the import tag :prio
272to get then):
110 273
111=cut 274 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
275 3 > 1 > 0 > -1 > -3 > -4
112 276
113$error_msg = 277 # set priority to HIGH
114$error_coro = undef; 278 current->prio(PRIO_HIGH);
115 279
116$error = _newprocess { 280The idle coroutine ($Coro::idle) always has a lower priority than any
117 print STDERR "FATAL: $error_msg\nprogram aborted\n"; 281existing coroutine.
118 exit 50; 282
119}; 283Changing the priority of the current process will take effect immediately,
284but changing the priority of processes in the ready queue (but not
285running) will only take effect after the next schedule (of that
286process). This is a bug that will be fixed in some future version.
287
288=cut
289
290sub prio {
291 my $old = $_[0]{prio};
292 $_[0]{prio} = $_[1] if @_ > 1;
293 $old;
294}
295
296=item $newprio = $process->nice($change)
297
298Similar to C<prio>, but subtract the given value from the priority (i.e.
299higher values mean lower priority, just as in unix).
300
301=cut
302
303sub nice {
304 $_[0]{prio} -= $_[1];
305}
306
307=item $olddesc = $process->desc($newdesc)
308
309Sets (or gets in case the argument is missing) the description for this
310process. This is just a free-form string you can associate with a process.
311
312=cut
313
314sub desc {
315 my $old = $_[0]{desc};
316 $_[0]{desc} = $_[1] if @_ > 1;
317 $old;
318}
319
320=back
321
322=cut
120 323
1211; 3241;
122 325
123=back 326=head1 BUGS/LIMITATIONS
124 327
125=head1 BUGS 328 - you must make very sure that no coro is still active on global destruction.
126 329 very bad things might happen otherwise (usually segfaults).
127This module has not yet been extensively tested. 330 - this module is not thread-safe. You must only ever use this module from
331 the same thread (this requirement might be loosened in the future to
332 allow per-thread schedulers, but Coro::State does not yet allow this).
128 333
129=head1 SEE ALSO 334=head1 SEE ALSO
130 335
131L<Coro::Process>, L<Coro::Signal>. 336L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
337L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
338L<Coro::Handle>, L<Coro::Socket>.
132 339
133=head1 AUTHOR 340=head1 AUTHOR
134 341
135 Marc Lehmann <pcg@goof.com> 342 Marc Lehmann <pcg@goof.com>
136 http://www.goof.com/pcg/marc/ 343 http://www.goof.com/pcg/marc/

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