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Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs.
Revision 1.37 by root, Mon Sep 24 02:25:44 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 = 0.5;
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 = new Coro sub {
122 while() {
123 # by overwriting the state object with the manager we destroy it
124 # while still being able to schedule this coroutine (in case it has
125 # been readied multiple times. this is harmless since the manager
126 # can be called as many times as neccessary and will always
127 # remove itself from the runqueue
128 (pop @destroy)->{_coro_state} = $manager->{_coro_state} while @destroy;
129 &schedule;
130 }
131};
132
133# static methods. not really.
134
135=head2 STATIC METHODS
136
137Static methods are actually functions that operate on the current process only.
34 138
35=over 4 139=over 4
36 140
37=cut 141=item async { ... } [@args...]
38 142
39package Coro; 143Create a new asynchronous process and return it's process object
144(usually unused). When the sub returns the new process is automatically
145terminated.
40 146
41BEGIN { 147 # create a new coroutine that just prints its arguments
42 $VERSION = 0.03; 148 async {
149 print "@_\n";
150 } 1,2,3,4;
43 151
44 require XSLoader; 152The coderef you submit MUST NOT be a closure that refers to variables
45 XSLoader::load Coro, $VERSION; 153in an outer scope. This does NOT work. Pass arguments into it instead.
46}
47 154
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 155=cut
156
157sub async(&@) {
158 my $pid = new Coro @_;
159 $manager->ready; # this ensures that the stack is cloned from the manager
160 $pid->ready;
161 $pid;
162}
163
164=item schedule
165
166Calls the scheduler. Please note that the current process will not be put
167into the ready queue, so calling this function usually means you will
168never be called again.
169
170=cut
171
172=item cede
173
174"Cede" to other processes. This function puts the current process into the
175ready queue and calls C<schedule>, which has the effect of giving up the
176current "timeslice" to other coroutines of the same or higher priority.
177
178=cut
179
180=item terminate
181
182Terminates the current process.
183
184Future versions of this function will allow result arguments.
185
186=cut
187
188sub terminate {
189 $current->cancel;
190 &schedule;
191 die; # NORETURN
192}
193
194=back
195
196# dynamic methods
197
198=head2 PROCESS METHODS
199
200These are the methods you can call on process objects.
201
202=over 4
203
204=item new Coro \&sub [, @args...]
205
206Create a new process and return it. When the sub returns the process
207automatically terminates. To start the process you must first put it into
208the ready queue by calling the ready method.
209
210The coderef you submit MUST NOT be a closure that refers to variables
211in an outer scope. This does NOT work. Pass arguments into it instead.
212
213=cut
214
215sub _newcoro {
216 terminate &{+shift};
217}
59 218
60sub new { 219sub new {
61 my $class = $_[0]; 220 my $class = shift;
62 my $proc = $_[1] || sub { die "tried to transfer to an empty coroutine" }; 221 bless {
63 bless _newprocess { 222 _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; 223 }, $class;
73} 224}
74 225
75=item $prev->transfer($next) 226=item $process->ready
76 227
77Save the state of the current subroutine in C<$prev> and switch to the 228Put the current process into the ready queue.
78coroutine saved in C<$next>.
79 229
80The "state" of a subroutine only ever includes scope, i.e. lexical
81variables and the current execution state. It does not save/restore any
82global variables such as C<$_> 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 230=cut
96 231
97# I call the _transfer function from a perl function 232=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}
104 233
105=item $error, $error_msg, $error_coro 234Like C<terminate>, but terminates the specified process instead.
106 235
107This coroutine will be called on fatal errors. C<$error_msg> and
108C<$error_coro> return the error message and the error-causing coroutine
109(NOT an object) respectively. This API might change.
110
111=cut 236=cut
112 237
113$error_msg = 238sub cancel {
114$error_coro = undef; 239 push @destroy, $_[0];
240 $manager->ready;
241 &schedule if $current == $_[0];
242}
115 243
116$error = _newprocess { 244=item $oldprio = $process->prio($newprio)
117 print STDERR "FATAL: $error_msg\nprogram aborted\n"; 245
118 exit 50; 246Sets the priority of the process. Higher priority processes get run before
119}; 247lower priority processes. Priorities are smalled signed integer (currently
248-4 .. +3), that you can refer to using PRIO_xxx constants (use the import
249tag :prio to get then):
250
251 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
252 3 > 1 > 0 > -1 > -3 > -4
253
254 # set priority to HIGH
255 current->prio(PRIO_HIGH);
256
257The idle coroutine ($Coro::idle) always has a lower priority than any
258existing coroutine.
259
260Changing the priority of the current process will take effect immediately,
261but changing the priority of processes in the ready queue (but not
262running) will only take effect after the next schedule (of that
263process). This is a bug that will be fixed in some future version.
264
265=cut
266
267sub prio {
268 my $old = $_[0]{prio};
269 $_[0]{prio} = $_[1] if @_ > 1;
270 $old;
271}
272
273=item $newprio = $process->nice($change)
274
275Similar to C<prio>, but subtract the given value from the priority (i.e.
276higher values mean lower priority, just as in unix).
277
278=cut
279
280sub nice {
281 $_[0]{prio} -= $_[1];
282}
283
284=back
285
286=cut
120 287
1211; 2881;
122 289
123=back 290=head1 BUGS/LIMITATIONS
124 291
125=head1 BUGS 292 - you must make very sure that no coro is still active on global destruction.
126 293 very bad things might happen otherwise (usually segfaults).
127This module has not yet been extensively tested. 294 - this module is not thread-safe. You must only ever use this module from
295 the same thread (this requirement might be loosened in the future to
296 allow per-thread schedulers, but Coro::State does not yet allow this).
128 297
129=head1 SEE ALSO 298=head1 SEE ALSO
130 299
131L<Coro::Process>, L<Coro::Signal>. 300L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
301L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
302L<Coro::Handle>, L<Coro::Socket>.
132 303
133=head1 AUTHOR 304=head1 AUTHOR
134 305
135 Marc Lehmann <pcg@goof.com> 306 Marc Lehmann <pcg@goof.com>
136 http://www.goof.com/pcg/marc/ 307 http://www.goof.com/pcg/marc/

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