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For /wise/base/deliv/dev/bin/getfix
  Run on Thu May 20 15:30:03 2010
Reported on Thu May 20 16:25:44 2010

File/wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3.pm
Statements Executed87
Total Time0.001893 seconds

Subroutines — ordered by exclusive time
Calls P F Exclusive
Time		 Inclusive
Time		 Subroutine
1010100.000140.00020Class::C3::import
00000Class::C3::BEGIN
00000Class::C3::__ANON__[:193]
00000Class::C3::_apply_method_dispatch_table
00000Class::C3::_apply_method_dispatch_tables
00000Class::C3::_calculate_method_dispatch_table
00000Class::C3::_calculate_method_dispatch_tables
00000Class::C3::_core_calculateMRO
00000Class::C3::_dump_MRO_table
00000Class::C3::_remove_method_dispatch_table
00000Class::C3::_remove_method_dispatch_tables
00000Class::C3::calculateMRO
00000Class::C3::initialize
00000Class::C3::reinitialize
00000Class::C3::uninitialize

LineStmts.Exclusive
Time		Avg.Code
1
2package Class::C3;
3
433.2e-51.1e-5use strict;
# spent 11µs making 1 call to strict::import
530.000196.4e-5use warnings;
# spent 49µs making 1 call to warnings::import
6
711.0e-61.0e-6our $VERSION = '0.19';
8
911.0e-61.0e-6our $C3_IN_CORE;
10100our $C3_XS;
11
12BEGIN {
1312.0e-62.0e-6 if($] > 5.009_004) {
14100 $C3_IN_CORE = 1;
1510.000210.00021 require mro;
16 }
17 else {
18 eval "require Class::C3::XS";
19 my $error = $@;
20 if(!$error) {
21 $C3_XS = 1;
22 }
23 else {
24 die $error if $error !~ /\blocate\b/;
25 require Algorithm::C3;
26 require Class::C3::next;
27 }
28 }
2910.000400.00040}
30
31# this is our global stash of both
32# MRO's and method dispatch tables
33# the structure basically looks like
34# this:
35#
36# $MRO{$class} = {
37# MRO => [ <class precendence list> ],
38# methods => {
39# orig => <original location of method>,
40# code => \&<ref to original method>
41# },
42# has_overload_fallback => (1 | 0)
43# }
44#
4511.0e-61.0e-6our %MRO;
46
47# use these for debugging ...
48sub _dump_MRO_table { %MRO }
4911.0e-61.0e-6our $TURN_OFF_C3 = 0;
50
51# state tracking for initialize()/uninitialize()
52100our $_initialized = 0;
53
54
# spent 200µs (137+63) within Class::C3::import which was called 10 times, avg 20µs/call: # once (26µs+6µs) at line 1 of (eval 75)[/wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm:180] at line 180 of /wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm # once (13µs+17µs) at line 43 of /wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm # once (15µs+5µs) at line 1 of (eval 131)[/wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm:180] at line 180 of /wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm # once (14µs+5µs) at line 1 of (eval 80)[/wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm:180] at line 180 of /wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm # once (13µs+6µs) at line 1 of (eval 107)[/wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm:180] at line 180 of /wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm # once (12µs+5µs) at line 1 of (eval 186)[/wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm:180] at line 180 of /wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm # once (12µs+5µs) at line 1 of (eval 181)[/wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm:180] at line 180 of /wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm # once (11µs+5µs) at line 1 of (eval 191)[/wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm:180] at line 180 of /wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm # once (12µs+4µs) at line 1 of (eval 110)[/wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm:180] at line 180 of /wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm # once (9µs+5µs) at line 1 of (eval 111)[/wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm:180] at line 180 of /wise/base/static/lib/perl5/site_perl/5.10.0/Class/C3/Componentised.pm
sub import {
55101.3e-51.3e-6 my $class = caller();
56 # skip if the caller is main::
57 # since that is clearly not relevant
58105.0e-65.0e-7 return if $class eq 'main';
59
60106.0e-66.0e-7 return if $TURN_OFF_C3;
61107.8e-57.8e-6 mro::set_mro($class, 'c3') if $C3_IN_CORE;
# spent 63µs making 10 calls to mro::set_mro, avg 6µs/call
62
63 # make a note to calculate $class
64 # during INIT phase
65102.8e-52.8e-6 $MRO{$class} = undef unless exists $MRO{$class};
66}
67
68## initializers
69
70sub initialize {
71 %next::METHOD_CACHE = ();
72 # why bother if we don't have anything ...
73 return unless keys %MRO;
74 if($C3_IN_CORE) {
75 mro::set_mro($_, 'c3') for keys %MRO;
76 }
77 else {
78 if($_initialized) {
79 uninitialize();
80 $MRO{$_} = undef foreach keys %MRO;
81 }
82 _calculate_method_dispatch_tables();
83 _apply_method_dispatch_tables();
84 $_initialized = 1;
85 }
86}
87
88sub uninitialize {
89 # why bother if we don't have anything ...
90 %next::METHOD_CACHE = ();
91 return unless keys %MRO;
92 if($C3_IN_CORE) {
93 mro::set_mro($_, 'dfs') for keys %MRO;
94 }
95 else {
96 _remove_method_dispatch_tables();
97 $_initialized = 0;
98 }
99}
100
101sub reinitialize { goto &initialize }
102
103## functions for applying C3 to classes
104
105sub _calculate_method_dispatch_tables {
106 return if $C3_IN_CORE;
107 my %merge_cache;
108 foreach my $class (keys %MRO) {
109 _calculate_method_dispatch_table($class, \%merge_cache);
110 }
111}
112
113sub _calculate_method_dispatch_table {
114 return if $C3_IN_CORE;
115 my ($class, $merge_cache) = @_;
11630.000289.4e-5 no strict 'refs';
# spent 21µs making 1 call to strict::unimport
117 my @MRO = calculateMRO($class, $merge_cache);
118 $MRO{$class} = { MRO => \@MRO };
119 my $has_overload_fallback;
120 my %methods;
121 # NOTE:
122 # we do @MRO[1 .. $#MRO] here because it
123 # makes no sense to interogate the class
124 # which you are calculating for.
125 foreach my $local (@MRO[1 .. $#MRO]) {
126 # if overload has tagged this module to
127 # have use "fallback", then we want to
128 # grab that value
129 $has_overload_fallback = ${"${local}::()"}
130 if !defined $has_overload_fallback && defined ${"${local}::()"};
131 foreach my $method (grep { defined &{"${local}::$_"} } keys %{"${local}::"}) {
132 # skip if already overriden in local class
133 next unless !defined *{"${class}::$method"}{CODE};
134 $methods{$method} = {
135 orig => "${local}::$method",
136 code => \&{"${local}::$method"}
137 } unless exists $methods{$method};
138 }
139 }
140 # now stash them in our %MRO table
141 $MRO{$class}->{methods} = \%methods;
142 $MRO{$class}->{has_overload_fallback} = $has_overload_fallback;
143}
144
145sub _apply_method_dispatch_tables {
146 return if $C3_IN_CORE;
147 foreach my $class (keys %MRO) {
148 _apply_method_dispatch_table($class);
149 }
150}
151
152sub _apply_method_dispatch_table {
153 return if $C3_IN_CORE;
154 my $class = shift;
15530.000247.9e-5 no strict 'refs';
# spent 19µs making 1 call to strict::unimport
156 ${"${class}::()"} = $MRO{$class}->{has_overload_fallback}
157 if !defined &{"${class}::()"}
158 && defined $MRO{$class}->{has_overload_fallback};
159 foreach my $method (keys %{$MRO{$class}->{methods}}) {
160 if ( $method =~ /^\(/ ) {
161 my $orig = $MRO{$class}->{methods}->{$method}->{orig};
162 ${"${class}::$method"} = $$orig if defined $$orig;
163 }
164 *{"${class}::$method"} = $MRO{$class}->{methods}->{$method}->{code};
165 }
166}
167
168sub _remove_method_dispatch_tables {
169 return if $C3_IN_CORE;
170 foreach my $class (keys %MRO) {
171 _remove_method_dispatch_table($class);
172 }
173}
174
175sub _remove_method_dispatch_table {
176 return if $C3_IN_CORE;
177 my $class = shift;
17830.000165.4e-5 no strict 'refs';
# spent 22µs making 1 call to strict::unimport
179 delete ${"${class}::"}{"()"} if $MRO{$class}->{has_overload_fallback};
180 foreach my $method (keys %{$MRO{$class}->{methods}}) {
181 delete ${"${class}::"}{$method}
182 if defined *{"${class}::${method}"}{CODE} &&
183 (*{"${class}::${method}"}{CODE} eq $MRO{$class}->{methods}->{$method}->{code});
184 }
185}
186
187sub calculateMRO {
188 my ($class, $merge_cache) = @_;
189
190 return Algorithm::C3::merge($class, sub {
19130.000103.5e-5 no strict 'refs';
# spent 19µs making 1 call to strict::unimport
192 @{$_[0] . '::ISA'};
193 }, $merge_cache);
194}
195
196# Method overrides to support 5.9.5+ or Class::C3::XS
197
198sub _core_calculateMRO { @{mro::get_linear_isa($_[0], 'c3')} }
199
20011.0e-61.0e-6if($C3_IN_CORE) {
20136.3e-52.1e-5 no warnings 'redefine';
# spent 29µs making 1 call to warnings::unimport
20218.0e-68.0e-6 *Class::C3::calculateMRO = \&_core_calculateMRO;
203}
204elsif($C3_XS) {
20536.1e-52.0e-5 no warnings 'redefine';
# spent 27µs making 1 call to warnings::unimport
206 *Class::C3::calculateMRO = \&Class::C3::XS::calculateMRO;
207 *Class::C3::_calculate_method_dispatch_table
208 = \&Class::C3::XS::_calculate_method_dispatch_table;
209}
210
21118.0e-68.0e-61;
212
213__END__
214
215=pod
216
217=head1 NAME
218
219Class::C3 - A pragma to use the C3 method resolution order algortihm
220
221=head1 SYNOPSIS
222
223 package A;
224 use Class::C3;
225 sub hello { 'A::hello' }
226
227 package B;
228 use base 'A';
229 use Class::C3;
230
231 package C;
232 use base 'A';
233 use Class::C3;
234
235 sub hello { 'C::hello' }
236
237 package D;
238 use base ('B', 'C');
239 use Class::C3;
240
241 # Classic Diamond MI pattern
242 # <A>
243 # / \
244 # <B> <C>
245 # \ /
246 # <D>
247
248 package main;
249
250 # initializez the C3 module
251 # (formerly called in INIT)
252 Class::C3::initialize();
253
254 print join ', ' => Class::C3::calculateMRO('Diamond_D') # prints D, B, C, A
255
256 print D->hello() # prints 'C::hello' instead of the standard p5 'A::hello'
257
258 D->can('hello')->(); # can() also works correctly
259 UNIVERSAL::can('D', 'hello'); # as does UNIVERSAL::can()
260
261=head1 DESCRIPTION
262
263This is pragma to change Perl 5's standard method resolution order from depth-first left-to-right
264(a.k.a - pre-order) to the more sophisticated C3 method resolution order.
265
266=head2 What is C3?
267
268C3 is the name of an algorithm which aims to provide a sane method resolution order under multiple
269inheritence. It was first introduced in the langauge Dylan (see links in the L<SEE ALSO> section),
270and then later adopted as the prefered MRO (Method Resolution Order) for the new-style classes in
271Python 2.3. Most recently it has been adopted as the 'canonical' MRO for Perl 6 classes, and the
272default MRO for Parrot objects as well.
273
274=head2 How does C3 work.
275
276C3 works by always preserving local precendence ordering. This essentially means that no class will
277appear before any of it's subclasses. Take the classic diamond inheritence pattern for instance:
278
279 <A>
280 / \
281 <B> <C>
282 \ /
283 <D>
284
285The standard Perl 5 MRO would be (D, B, A, C). The result being that B<A> appears before B<C>, even
286though B<C> is the subclass of B<A>. The C3 MRO algorithm however, produces the following MRO
287(D, B, C, A), which does not have this same issue.
288
289This example is fairly trival, for more complex examples and a deeper explaination, see the links in
290the L<SEE ALSO> section.
291
292=head2 How does this module work?
293
294This module uses a technique similar to Perl 5's method caching. When C<Class::C3::initialize> is
295called, this module calculates the MRO of all the classes which called C<use Class::C3>. It then
296gathers information from the symbol tables of each of those classes, and builds a set of method
297aliases for the correct dispatch ordering. Once all these C3-based method tables are created, it
298then adds the method aliases into the local classes symbol table.
299
300The end result is actually classes with pre-cached method dispatch. However, this caching does not
301do well if you start changing your C<@ISA> or messing with class symbol tables, so you should consider
302your classes to be effectively closed. See the L<CAVEATS> section for more details.
303
304=head1 OPTIONAL LOWERCASE PRAGMA
305
306This release also includes an optional module B<c3> in the F<opt/> folder. I did not include this in
307the regular install since lowercase module names are considered I<"bad"> by some people. However I
308think that code looks much nicer like this:
309
310 package MyClass;
311 use c3;
312
313The the more clunky:
314
315 package MyClass;
316 use Class::C3;
317
318But hey, it's your choice, thats why it is optional.
319
320=head1 FUNCTIONS
321
322=over 4
323
324=item B<calculateMRO ($class)>
325
326Given a C<$class> this will return an array of class names in the proper C3 method resolution order.
327
328=item B<initialize>
329
330This B<must be called> to initalize the C3 method dispatch tables, this module B<will not work> if
331you do not do this. It is advised to do this as soon as possible B<after> loading any classes which
332use C3. Here is a quick code example:
333
334 package Foo;
335 use Class::C3;
336 # ... Foo methods here
337
338 package Bar;
339 use Class::C3;
340 use base 'Foo';
341 # ... Bar methods here
342
343 package main;
344
345 Class::C3::initialize(); # now it is safe to use Foo and Bar
346
347This function used to be called automatically for you in the INIT phase of the perl compiler, but
348that lead to warnings if this module was required at runtime. After discussion with my user base
349(the L<DBIx::Class> folks), we decided that calling this in INIT was more of an annoyance than a
350convience. I apologize to anyone this causes problems for (although i would very suprised if I had
351any other users other than the L<DBIx::Class> folks). The simplest solution of course is to define
352your own INIT method which calls this function.
353
354NOTE:
355
356If C<initialize> detects that C<initialize> has already been executed, it will L</uninitialize> and
357clear the MRO cache first.
358
359=item B<uninitialize>
360
361Calling this function results in the removal of all cached methods, and the restoration of the old Perl 5
362style dispatch order (depth-first, left-to-right).
363
364=item B<reinitialize>
365
366This is an alias for L</initialize> above.
367
368=back
369
370=head1 METHOD REDISPATCHING
371
372It is always useful to be able to re-dispatch your method call to the "next most applicable method". This
373module provides a pseudo package along the lines of C<SUPER::> or C<NEXT::> which will re-dispatch the
374method along the C3 linearization. This is best show with an examples.
375
376 # a classic diamond MI pattern ...
377 <A>
378 / \
379 <B> <C>
380 \ /
381 <D>
382
383 package A;
384 use c3;
385 sub foo { 'A::foo' }
386
387 package B;
388 use base 'A';
389 use c3;
390 sub foo { 'B::foo => ' . (shift)->next::method() }
391
392 package B;
393 use base 'A';
394 use c3;
395 sub foo { 'C::foo => ' . (shift)->next::method() }
396
397 package D;
398 use base ('B', 'C');
399 use c3;
400 sub foo { 'D::foo => ' . (shift)->next::method() }
401
402 print D->foo; # prints out "D::foo => B::foo => C::foo => A::foo"
403
404A few things to note. First, we do not require you to add on the method name to the C<next::method>
405call (this is unlike C<NEXT::> and C<SUPER::> which do require that). This helps to enforce the rule
406that you cannot dispatch to a method of a different name (this is how C<NEXT::> behaves as well).
407
408The next thing to keep in mind is that you will need to pass all arguments to C<next::method> it can
409not automatically use the current C<@_>.
410
411If C<next::method> cannot find a next method to re-dispatch the call to, it will throw an exception.
412You can use C<next::can> to see if C<next::method> will succeed before you call it like so:
413
414 $self->next::method(@_) if $self->next::can;
415
416Additionally, you can use C<maybe::next::method> as a shortcut to only call the next method if it exists.
417The previous example could be simply written as:
418
419 $self->maybe::next::method(@_);
420
421There are some caveats about using C<next::method>, see below for those.
422
423=head1 CAVEATS
424
425This module used to be labeled as I<experimental>, however it has now been pretty heavily tested by
426the good folks over at L<DBIx::Class> and I am confident this module is perfectly usable for
427whatever your needs might be.
428
429But there are still caveats, so here goes ...
430
431=over 4
432
433=item Use of C<SUPER::>.
434
435The idea of C<SUPER::> under multiple inheritence is ambigious, and generally not recomended anyway.
436However, it's use in conjuntion with this module is very much not recommended, and in fact very
437discouraged. The recommended approach is to instead use the supplied C<next::method> feature, see
438more details on it's usage above.
439
440=item Changing C<@ISA>.
441
442It is the author's opinion that changing C<@ISA> at runtime is pure insanity anyway. However, people
443do it, so I must caveat. Any changes to the C<@ISA> will not be reflected in the MRO calculated by this
444module, and therefor probably won't even show up. If you do this, you will need to call C<reinitialize>
445in order to recalulate B<all> method dispatch tables. See the C<reinitialize> documentation and an example
446in F<t/20_reinitialize.t> for more information.
447
448=item Adding/deleting methods from class symbol tables.
449
450This module calculates the MRO for each requested class by interogatting the symbol tables of said classes.
451So any symbol table manipulation which takes place after our INIT phase is run will not be reflected in
452the calculated MRO. Just as with changing the C<@ISA>, you will need to call C<reinitialize> for any
453changes you make to take effect.
454
455=item Calling C<next::method> from methods defined outside the class
456
457There is an edge case when using C<next::method> from within a subroutine which was created in a different
458module than the one it is called from. It sounds complicated, but it really isn't. Here is an example which
459will not work correctly:
460
461 *Foo::foo = sub { (shift)->next::method(@_) };
462
463The problem exists because the anonymous subroutine being assigned to the glob C<*Foo::foo> will show up
464in the call stack as being called C<__ANON__> and not C<foo> as you might expect. Since C<next::method>
465uses C<caller> to find the name of the method it was called in, it will fail in this case.
466
467But fear not, there is a simple solution. The module C<Sub::Name> will reach into the perl internals and
468assign a name to an anonymous subroutine for you. Simply do this:
469
470 use Sub::Name 'subname';
471 *Foo::foo = subname 'Foo::foo' => sub { (shift)->next::method(@_) };
472
473and things will Just Work. Of course this is not always possible to do, but to be honest, I just can't
474manage to find a workaround for it, so until someone gives me a working patch this will be a known
475limitation of this module.
476
477=back
478
479=head1 COMPATIBILITY
480
481If your software requires Perl 5.9.5 or higher, you do not need L<Class::C3>, you can simply C<use mro 'c3'>, and not worry about C<initialize()>, avoid some of the above caveats, and get the best possible performance. See L<mro> for more details.
482
483If your software is meant to work on earlier Perls, use L<Class::C3> as documented here. L<Class::C3> will detect Perl 5.9.5+ and take advantage of the core support when available.
484
485=head1 Class::C3::XS
486
487This module will load L<Class::C3::XS> if it's installed and you are running on a Perl version older than 5.9.5. Installing this is recommended when possible, as it results in significant performance improvements (but unlike the 5.9.5+ core support, it still has all of the same caveats as L<Class::C3>).
488
489=head1 CODE COVERAGE
490
491L<Devel::Cover> was reporting 94.4% overall test coverage earlier in this module's life. Currently, the test suite does things that break under coverage testing, but it is fair to assume the coverage is still close to that value.
492
493=head1 SEE ALSO
494
495=head2 The original Dylan paper
496
497=over 4
498
499=item L<http://www.webcom.com/haahr/dylan/linearization-oopsla96.html>
500
501=back
502
503=head2 The prototype Perl 6 Object Model uses C3
504
505=over 4
506
507=item L<http://svn.openfoundry.org/pugs/perl5/Perl6-MetaModel/>
508
509=back
510
511=head2 Parrot now uses C3
512
513=over 4
514
515=item L<http://aspn.activestate.com/ASPN/Mail/Message/perl6-internals/2746631>
516
517=item L<http://use.perl.org/~autrijus/journal/25768>
518
519=back
520
521=head2 Python 2.3 MRO related links
522
523=over 4
524
525=item L<http://www.python.org/2.3/mro.html>
526
527=item L<http://www.python.org/2.2.2/descrintro.html#mro>
528
529=back
530
531=head2 C3 for TinyCLOS
532
533=over 4
534
535=item L<http://www.call-with-current-continuation.org/eggs/c3.html>
536
537=back
538
539=head1 ACKNOWLEGEMENTS
540
541=over 4
542
543=item Thanks to Matt S. Trout for using this module in his module L<DBIx::Class>
544and finding many bugs and providing fixes.
545
546=item Thanks to Justin Guenther for making C<next::method> more robust by handling
547calls inside C<eval> and anon-subs.
548
549=item Thanks to Robert Norris for adding support for C<next::can> and
550C<maybe::next::method>.
551
552=back
553
554=head1 AUTHOR
555
556Stevan Little, E<lt>stevan@iinteractive.comE<gt>
557
558Brandon L. Black, E<lt>blblack@gmail.comE<gt>
559
560=head1 COPYRIGHT AND LICENSE
561
562Copyright 2005, 2006 by Infinity Interactive, Inc.
563
564L<http://www.iinteractive.com>
565
566This library is free software; you can redistribute it and/or modify
567it under the same terms as Perl itself.
568
569=cut

Report produced by the NYTProf 2.07 Perl profiler, developed by Tim Bunce and Adam Kaplan.