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Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs.
Revision 1.39 by root, Tue Oct 9 00:39:08 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 = 0.51;
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 (pop @destroy)->{_coro_state} = $manager->{_coro_state} while @destroy;
130 &schedule;
131 }
132};
133
134# static methods. not really.
135
136=head2 STATIC METHODS
137
138Static methods are actually functions that operate on the current process only.
34 139
35=over 4 140=over 4
36 141
37=cut 142=item async { ... } [@args...]
38 143
39package Coro; 144Create a new asynchronous process and return it's process object
145(usually unused). When the sub returns the new process is automatically
146terminated.
40 147
41BEGIN { 148 # create a new coroutine that just prints its arguments
42 $VERSION = 0.03; 149 async {
150 print "@_\n";
151 } 1,2,3,4;
43 152
44 require XSLoader; 153The coderef you submit MUST NOT be a closure that refers to variables
45 XSLoader::load Coro, $VERSION; 154in an outer scope. This does NOT work. Pass arguments into it instead.
46}
47 155
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 156=cut
157
158sub async(&@) {
159 my $pid = new Coro @_;
160 $manager->ready; # this ensures that the stack is cloned from the manager
161 $pid->ready;
162 $pid;
163}
164
165=item schedule
166
167Calls the scheduler. Please note that the current process will not be put
168into the ready queue, so calling this function usually means you will
169never be called again.
170
171=cut
172
173=item cede
174
175"Cede" to other processes. This function puts the current process into the
176ready queue and calls C<schedule>, which has the effect of giving up the
177current "timeslice" to other coroutines of the same or higher priority.
178
179=cut
180
181=item terminate
182
183Terminates the current process.
184
185Future versions of this function will allow result arguments.
186
187=cut
188
189sub terminate {
190 $current->cancel;
191 &schedule;
192 die; # NORETURN
193}
194
195=back
196
197# dynamic methods
198
199=head2 PROCESS METHODS
200
201These are the methods you can call on process objects.
202
203=over 4
204
205=item new Coro \&sub [, @args...]
206
207Create a new process and return it. When the sub returns the process
208automatically terminates. To start the process you must first put it into
209the ready queue by calling the ready method.
210
211The coderef you submit MUST NOT be a closure that refers to variables
212in an outer scope. This does NOT work. Pass arguments into it instead.
213
214=cut
215
216sub _newcoro {
217 terminate &{+shift};
218}
59 219
60sub new { 220sub new {
61 my $class = $_[0]; 221 my $class = shift;
62 my $proc = $_[1] || sub { die "tried to transfer to an empty coroutine" }; 222 bless {
63 bless _newprocess { 223 _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; 224 }, $class;
73} 225}
74 226
75=item $prev->transfer($next) 227=item $process->ready
76 228
77Save the state of the current subroutine in C<$prev> and switch to the 229Put the given process into the ready queue.
78coroutine saved in C<$next>.
79 230
80The "state" of a subroutine only ever includes scope, i.e. lexical
81variables and the current execution state. It does not save/restore any
82global variables such as C<$_> or C<$@> or any other special or non
83special variables. So remember that every function call that might call
84C<transfer> (such as C<Coro::Channel::put>) might clobber any global
85and/or special variables. Yes, this is by design ;) You cna always create
86your own process abstraction model that saves these variables.
87
88The easiest way to do this is to create your own scheduling primitive like this:
89
90 sub schedule {
91 local ($_, $@, ...);
92 $old->transfer($new);
93 }
94
95=cut 231=cut
96 232
97# I call the _transfer function from a perl function 233=item $process->cancel
98# because that way perl saves all important things on
99# the stack. Actually, I'd do it from within XS, but
100# I couldn't get it to work.
101sub transfer {
102 _transfer($_[0], $_[1]);
103}
104 234
105=item $error, $error_msg, $error_coro 235Like C<terminate>, but terminates the specified process instead.
106 236
107This coroutine will be called on fatal errors. C<$error_msg> and
108C<$error_coro> return the error message and the error-causing coroutine
109(NOT an object) respectively. This API might change.
110
111=cut 237=cut
112 238
113$error_msg = 239sub cancel {
114$error_coro = undef; 240 push @destroy, $_[0];
241 $manager->ready;
242 &schedule if $current == $_[0];
243}
115 244
116$error = _newprocess { 245=item $oldprio = $process->prio($newprio)
117 print STDERR "FATAL: $error_msg\nprogram aborted\n"; 246
118 exit 50; 247Sets the priority of the process. Higher priority processes get run before
119}; 248lower priority processes. Priorities are smalled signed integer (currently
249-4 .. +3), that you can refer to using PRIO_xxx constants (use the import
250tag :prio to get then):
251
252 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
253 3 > 1 > 0 > -1 > -3 > -4
254
255 # set priority to HIGH
256 current->prio(PRIO_HIGH);
257
258The idle coroutine ($Coro::idle) always has a lower priority than any
259existing coroutine.
260
261Changing the priority of the current process will take effect immediately,
262but changing the priority of processes in the ready queue (but not
263running) will only take effect after the next schedule (of that
264process). This is a bug that will be fixed in some future version.
265
266=cut
267
268sub prio {
269 my $old = $_[0]{prio};
270 $_[0]{prio} = $_[1] if @_ > 1;
271 $old;
272}
273
274=item $newprio = $process->nice($change)
275
276Similar to C<prio>, but subtract the given value from the priority (i.e.
277higher values mean lower priority, just as in unix).
278
279=cut
280
281sub nice {
282 $_[0]{prio} -= $_[1];
283}
284
285=back
286
287=cut
120 288
1211; 2891;
122 290
123=back 291=head1 BUGS/LIMITATIONS
124 292
125=head1 BUGS 293 - you must make very sure that no coro is still active on global destruction.
126 294 very bad things might happen otherwise (usually segfaults).
127This module has not yet been extensively tested. 295 - this module is not thread-safe. You must only ever use this module from
296 the same thread (this requirement might be loosened in the future to
297 allow per-thread schedulers, but Coro::State does not yet allow this).
128 298
129=head1 SEE ALSO 299=head1 SEE ALSO
130 300
131L<Coro::Process>, L<Coro::Signal>. 301L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
302L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
303L<Coro::Handle>, L<Coro::Socket>.
132 304
133=head1 AUTHOR 305=head1 AUTHOR
134 306
135 Marc Lehmann <pcg@goof.com> 307 Marc Lehmann <pcg@goof.com>
136 http://www.goof.com/pcg/marc/ 308 http://www.goof.com/pcg/marc/

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