use strict;
use warnings;
-our $VERSION = '0.01';
-
-use Scalar::Util 'blessed';
+our $VERSION = '0.15_01';
+
+our $C3_IN_CORE;
+
+BEGIN {
+ eval "require mro"; # XXX in the future, this should be a version check
+ if($@) {
+ die $@ if $@ !~ /locate/;
+# eval "require Class::C3::XS";
+# if($@) {
+# die $@ if $@ !~ /locate/;
+ eval "require Algorithm::C3; require Class::C3::next";
+ die $@ if $@;
+# }
+ }
+ else {
+ $C3_IN_CORE = 1;
+ }
+}
-my %MRO;
+# this is our global stash of both
+# MRO's and method dispatch tables
+# the structure basically looks like
+# this:
+#
+# $MRO{$class} = {
+# MRO => [ <class precendence list> ],
+# methods => {
+# orig => <original location of method>,
+# code => \&<ref to original method>
+# },
+# has_overload_fallback => (1 | 0)
+# }
+#
+our %MRO;
+
+# use these for debugging ...
+sub _dump_MRO_table { %MRO }
+our $TURN_OFF_C3 = 0;
+
+# state tracking for initialize()/uninitialize()
+our $_initialized = 0;
sub import {
my $class = caller();
+ # skip if the caller is main::
+ # since that is clearly not relevant
return if $class eq 'main';
- $MRO{$class} = undef;
+
+ return if $TURN_OFF_C3;
+ mro::set_mro($class, 'c3') if $C3_IN_CORE;
+
+ # make a note to calculate $class
+ # during INIT phase
+ $MRO{$class} = undef unless exists $MRO{$class};
}
-INIT {
- no strict 'refs';
- foreach my $class (keys %MRO) {
- my @MRO = calculateMRO($class);
- $MRO{$class} = { MRO => \@MRO };
- my %methods;
- foreach my $local (@MRO[1 .. $#MRO]) {
- foreach my $method (grep { defined &{"${local}::$_"} } keys %{"${local}::"}) {
- next unless !defined *{"${class}::$method"}{CODE};
- if (!exists $methods{$method}) {
- $methods{$method} = {
- orig => "${local}::$method",
- code => \&{"${local}::$method"}
- };
- }
- }
- }
- $MRO{$class}->{methods} = \%methods;
+## initializers
+
+sub initialize {
+ %next::METHOD_CACHE = ();
+ # why bother if we don't have anything ...
+ return unless keys %MRO;
+ if($C3_IN_CORE) {
+ mro::set_mro($_, 'c3') for keys %MRO;
}
- #use Data::Dumper; warn Dumper \%MRO;
- foreach my $class (keys %MRO) {
- #warn "installing methods (" . (join ", " => keys %{$MRO{$class}->{methods}}) . ") for $class";
- foreach my $method (keys %{$MRO{$class}->{methods}}) {
- #warn "Installing ${class}::$method using " . $MRO{$class}->{methods}->{$method}->{orig};
- *{"${class}::$method"} = $MRO{$class}->{methods}->{$method}->{code};
+ else {
+ if($_initialized) {
+ uninitialize();
+ $MRO{$_} = undef foreach keys %MRO;
}
- }
+ _calculate_method_dispatch_tables();
+ _apply_method_dispatch_tables();
+ $_initialized = 1;
+ }
}
-sub _merge {
- my (@seqs) = @_;
- my @res;
- while (1) {
- # remove all empty seqences
- my @nonemptyseqs = (map { (@{$_} ? $_ : ()) } @seqs);
- # return the list if we have no more no-empty sequences
- return @res if not @nonemptyseqs;
- my $cand; # a canidate ..
- foreach my $seq (@nonemptyseqs) {
- $cand = $seq->[0]; # get the head of the list
- my $nothead;
- foreach my $sub_seq (@nonemptyseqs) {
- # XXX - this is instead of the python "in"
- my %in_tail = (map { $_ => 1 } @{$sub_seq}[ 1 .. $#{$sub_seq} ]);
- # NOTE:
- # jump out as soon as we find one matching
- # there is no reason not too. However, if
- # we find one, then just remove the '&& last'
- $nothead++ && last if exists $in_tail{$cand};
- }
- last unless $nothead; # leave the loop with our canidate ...
- $cand = undef; # otherwise, reject it ...
- }
- die "Inconsistent hierarchy" if not $cand;
- push @res => $cand;
- # now loop through our non-empties and pop
- # off the head if it matches our canidate
- foreach my $seq (@nonemptyseqs) {
- shift @{$seq} if $seq->[0] eq $cand;
- }
+sub uninitialize {
+ # why bother if we don't have anything ...
+ %next::METHOD_CACHE = ();
+ return unless keys %MRO;
+ if($C3_IN_CORE) {
+ mro::set_mro($_, 'dfs') for keys %MRO;
+ }
+ else {
+ _remove_method_dispatch_tables();
+ $_initialized = 0;
}
}
-sub calculateMRO {
- my ($class) = @_;
+sub reinitialize { goto &initialize }
+
+## functions for applying C3 to classes
+
+sub _calculate_method_dispatch_tables {
+ return if $C3_IN_CORE;
+ my %merge_cache;
+ foreach my $class (keys %MRO) {
+ _calculate_method_dispatch_table($class, \%merge_cache);
+ }
+}
+
+sub _calculate_method_dispatch_table {
+ return if $C3_IN_CORE;
+ my ($class, $merge_cache) = @_;
+ no strict 'refs';
+ my @MRO = calculateMRO($class, $merge_cache);
+ $MRO{$class} = { MRO => \@MRO };
+ my $has_overload_fallback = 0;
+ my %methods;
+ # NOTE:
+ # we do @MRO[1 .. $#MRO] here because it
+ # makes no sense to interogate the class
+ # which you are calculating for.
+ foreach my $local (@MRO[1 .. $#MRO]) {
+ # if overload has tagged this module to
+ # have use "fallback", then we want to
+ # grab that value
+ $has_overload_fallback = ${"${local}::()"}
+ if defined ${"${local}::()"};
+ foreach my $method (grep { defined &{"${local}::$_"} } keys %{"${local}::"}) {
+ # skip if already overriden in local class
+ next unless !defined *{"${class}::$method"}{CODE};
+ $methods{$method} = {
+ orig => "${local}::$method",
+ code => \&{"${local}::$method"}
+ } unless exists $methods{$method};
+ }
+ }
+ # now stash them in our %MRO table
+ $MRO{$class}->{methods} = \%methods;
+ $MRO{$class}->{has_overload_fallback} = $has_overload_fallback;
+}
+
+sub _apply_method_dispatch_tables {
+ return if $C3_IN_CORE;
+ foreach my $class (keys %MRO) {
+ _apply_method_dispatch_table($class);
+ }
+}
+
+sub _apply_method_dispatch_table {
+ return if $C3_IN_CORE;
+ my $class = shift;
+ no strict 'refs';
+ ${"${class}::()"} = $MRO{$class}->{has_overload_fallback}
+ if $MRO{$class}->{has_overload_fallback};
+ foreach my $method (keys %{$MRO{$class}->{methods}}) {
+ *{"${class}::$method"} = $MRO{$class}->{methods}->{$method}->{code};
+ }
+}
+
+sub _remove_method_dispatch_tables {
+ return if $C3_IN_CORE;
+ foreach my $class (keys %MRO) {
+ _remove_method_dispatch_table($class);
+ }
+}
+
+sub _remove_method_dispatch_table {
+ return if $C3_IN_CORE;
+ my $class = shift;
no strict 'refs';
- return _merge(
- [ $class ], # the class we are linearizing
- (map { [ calculateMRO($_) ] } @{"${class}::ISA"}), # the MRO of all the superclasses
- [ @{"${class}::ISA"} ] # a list of all the superclasses
- );
+ delete ${"${class}::"}{"()"} if $MRO{$class}->{has_overload_fallback};
+ foreach my $method (keys %{$MRO{$class}->{methods}}) {
+ delete ${"${class}::"}{$method}
+ if defined *{"${class}::${method}"}{CODE} &&
+ (*{"${class}::${method}"}{CODE} eq $MRO{$class}->{methods}->{$method}->{code});
+ }
+}
+
+sub calculateMRO {
+ my ($class, $merge_cache) = @_;
+
+ return @{mro::get_linear_isa($class)} if $C3_IN_CORE;
+
+ return Algorithm::C3::merge($class, sub {
+ no strict 'refs';
+ @{$_[0] . '::ISA'};
+ }, $merge_cache);
}
1;
use Class::C3;
# Classic Diamond MI pattern
- # [ A ]
- # / \
- # [ B ] [ C ]
- # \ /
- # [ D ]
+ # <A>
+ # / \
+ # <B> <C>
+ # \ /
+ # <D>
package main;
+
+ # initializez the C3 module
+ # (formerly called in INIT)
+ Class::C3::initialize();
print join ', ' => Class::C3::calculateMRO('Diamond_D') # prints D, B, C, A
D->can('hello')->(); # can() also works correctly
UNIVERSAL::can('D', 'hello'); # as does UNIVERSAL::can()
+=head1 SPECIAL NOTE FOR 0.15_01
+
+To try this with the experimental perl core c3 patch,
+download a recent copy perl-current:
+
+http://mirrors.develooper.com/perl/APC/perl-current-snap/perl-current@30943.tar.bz2
+
+apply the enclosed c3.patch, and install this perl:
+
+sh Configure -Dusedevel -Dprefix=/where/I/want/it -d -e && make && make test && make install
+
+then try your C3-using software against this perl + Class::C3 0.15_01.
+
=head1 DESCRIPTION
-This is currently an experimental pragma to change Perl 5's standard method resolution order
-from depth-first left-to-right (a.k.a - pre-order) to the more sophisticated C3 method resolution
-order.
+This is pragma to change Perl 5's standard method resolution order from depth-first left-to-right
+(a.k.a - pre-order) to the more sophisticated C3 method resolution order.
=head2 What is C3?
C3 works by always preserving local precendence ordering. This essentially means that no class will
appear before any of it's subclasses. Take the classic diamond inheritence pattern for instance:
- [ A ]
- / \
- [ B ] [ C ]
- \ /
- [ D ]
+ <A>
+ / \
+ <B> <C>
+ \ /
+ <D>
The standard Perl 5 MRO would be (D, B, A, C). The result being that B<A> appears before B<C>, even
though B<C> is the subclass of B<A>. The C3 MRO algorithm however, produces the following MRO
=head2 How does this module work?
-This module uses a technique similar to Perl 5's method caching. During the INIT phase, this module
-calculates the MRO of all the classes which called C<use Class::C3>. It then gathers information from
-the symbol tables of each of those classes, and builds a set of method aliases for the correct
-dispatch ordering. Once all these C3-based method tables are created, it then adds the method aliases
-into the local classes symbol table.
+This module uses a technique similar to Perl 5's method caching. When C<Class::C3::initialize> is
+called, this module calculates the MRO of all the classes which called C<use Class::C3>. It then
+gathers information from the symbol tables of each of those classes, and builds a set of method
+aliases for the correct dispatch ordering. Once all these C3-based method tables are created, it
+then adds the method aliases into the local classes symbol table.
The end result is actually classes with pre-cached method dispatch. However, this caching does not
do well if you start changing your C<@ISA> or messing with class symbol tables, so you should consider
your classes to be effectively closed. See the L<CAVEATS> section for more details.
+=head1 OPTIONAL LOWERCASE PRAGMA
+
+This release also includes an optional module B<c3> in the F<opt/> folder. I did not include this in
+the regular install since lowercase module names are considered I<"bad"> by some people. However I
+think that code looks much nicer like this:
+
+ package MyClass;
+ use c3;
+
+The the more clunky:
+
+ package MyClass;
+ use Class::C3;
+
+But hey, it's your choice, thats why it is optional.
+
=head1 FUNCTIONS
=over 4
Given a C<$class> this will return an array of class names in the proper C3 method resolution order.
+=item B<initialize>
+
+This B<must be called> to initalize the C3 method dispatch tables, this module B<will not work> if
+you do not do this. It is advised to do this as soon as possible B<after> loading any classes which
+use C3. Here is a quick code example:
+
+ package Foo;
+ use Class::C3;
+ # ... Foo methods here
+
+ package Bar;
+ use Class::C3;
+ use base 'Foo';
+ # ... Bar methods here
+
+ package main;
+
+ Class::C3::initialize(); # now it is safe to use Foo and Bar
+
+This function used to be called automatically for you in the INIT phase of the perl compiler, but
+that lead to warnings if this module was required at runtime. After discussion with my user base
+(the L<DBIx::Class> folks), we decided that calling this in INIT was more of an annoyance than a
+convience. I apologize to anyone this causes problems for (although i would very suprised if I had
+any other users other than the L<DBIx::Class> folks). The simplest solution of course is to define
+your own INIT method which calls this function.
+
+NOTE:
+
+If C<initialize> detects that C<initialize> has already been executed, it will L</uninitialize> and
+clear the MRO cache first.
+
+=item B<uninitialize>
+
+Calling this function results in the removal of all cached methods, and the restoration of the old Perl 5
+style dispatch order (depth-first, left-to-right).
+
+=item B<reinitialize>
+
+This is an alias for L</initialize> above.
+
=back
-=head1 CAVEATS
+=head1 METHOD REDISPATCHING
+
+It is always useful to be able to re-dispatch your method call to the "next most applicable method". This
+module provides a pseudo package along the lines of C<SUPER::> or C<NEXT::> which will re-dispatch the
+method along the C3 linearization. This is best show with an examples.
+
+ # a classic diamond MI pattern ...
+ <A>
+ / \
+ <B> <C>
+ \ /
+ <D>
+
+ package A;
+ use c3;
+ sub foo { 'A::foo' }
+
+ package B;
+ use base 'A';
+ use c3;
+ sub foo { 'B::foo => ' . (shift)->next::method() }
+
+ package B;
+ use base 'A';
+ use c3;
+ sub foo { 'C::foo => ' . (shift)->next::method() }
+
+ package D;
+ use base ('B', 'C');
+ use c3;
+ sub foo { 'D::foo => ' . (shift)->next::method() }
+
+ print D->foo; # prints out "D::foo => B::foo => C::foo => A::foo"
+
+A few things to note. First, we do not require you to add on the method name to the C<next::method>
+call (this is unlike C<NEXT::> and C<SUPER::> which do require that). This helps to enforce the rule
+that you cannot dispatch to a method of a different name (this is how C<NEXT::> behaves as well).
+
+The next thing to keep in mind is that you will need to pass all arguments to C<next::method> it can
+not automatically use the current C<@_>.
+
+If C<next::method> cannot find a next method to re-dispatch the call to, it will throw an exception.
+You can use C<next::can> to see if C<next::method> will succeed before you call it like so:
+
+ $self->next::method(@_) if $self->next::can;
+
+Additionally, you can use C<maybe::next::method> as a shortcut to only call the next method if it exists.
+The previous example could be simply written as:
+
+ $self->maybe::next::method(@_);
+
+There are some caveats about using C<next::method>, see below for those.
-Let me first say, this is an experimental module, and so it should not be used for anything other
-then other experimentation for the time being.
+=head1 CAVEATS
-That said, it is the authors intention to make this into a completely usable and production stable
-module if possible. Time will tell.
+This module used to be labeled as I<experimental>, however it has now been pretty heavily tested by
+the good folks over at L<DBIx::Class> and I am confident this module is perfectly usable for
+whatever your needs might be.
-And now, onto the caveats.
+But there are still caveats, so here goes ...
=over 4
The idea of C<SUPER::> under multiple inheritence is ambigious, and generally not recomended anyway.
However, it's use in conjuntion with this module is very much not recommended, and in fact very
-discouraged. In the future I plan to support a C<NEXT::> style interface to be used to move to the
-next most appropriate method in the MRO.
+discouraged. The recommended approach is to instead use the supplied C<next::method> feature, see
+more details on it's usage above.
=item Changing C<@ISA>.
It is the author's opinion that changing C<@ISA> at runtime is pure insanity anyway. However, people
do it, so I must caveat. Any changes to the C<@ISA> will not be reflected in the MRO calculated by this
-module, and therefor probably won't even show up. I am considering some kind of C<recalculateMRO> function
-which can be used to recalculate the MRO on demand at runtime, but that is still off in the future.
+module, and therefor probably won't even show up. If you do this, you will need to call C<reinitialize>
+in order to recalulate B<all> method dispatch tables. See the C<reinitialize> documentation and an example
+in F<t/20_reinitialize.t> for more information.
=item Adding/deleting methods from class symbol tables.
-This module calculates the MRO for each requested class during the INIT phase by interogatting the symbol
-tables of said classes. So any symbol table manipulation which takes place after our INIT phase is run will
-not be reflected in the calculated MRO.
+This module calculates the MRO for each requested class by interogatting the symbol tables of said classes.
+So any symbol table manipulation which takes place after our INIT phase is run will not be reflected in
+the calculated MRO. Just as with changing the C<@ISA>, you will need to call C<reinitialize> for any
+changes you make to take effect.
+
+=item Calling C<next::method> from methods defined outside the class
+
+There is an edge case when using C<next::method> from within a subroutine which was created in a different
+module than the one it is called from. It sounds complicated, but it really isn't. Here is an example which
+will not work correctly:
+
+ *Foo::foo = sub { (shift)->next::method(@_) };
-=item Not for use with mod_perl
+The problem exists because the anonymous subroutine being assigned to the glob C<*Foo::foo> will show up
+in the call stack as being called C<__ANON__> and not C<foo> as you might expect. Since C<next::method>
+uses C<caller> to find the name of the method it was called in, it will fail in this case.
-Since this module utilizes the INIT phase, it cannot be easily used with mod_perl. If this module works out
-and proves useful in the I<real world>, I will most likely be supporting mod_perl in some way.
+But fear not, there is a simple solution. The module C<Sub::Name> will reach into the perl internals and
+assign a name to an anonymous subroutine for you. Simply do this:
+
+ use Sub::Name 'subname';
+ *Foo::foo = subname 'Foo::foo' => sub { (shift)->next::method(@_) };
+
+and things will Just Work. Of course this is not always possible to do, but to be honest, I just can't
+manage to find a workaround for it, so until someone gives me a working patch this will be a known
+limitation of this module.
=back
+=head1 CODE COVERAGE
+
+I use B<Devel::Cover> to test the code coverage of my tests, below is the B<Devel::Cover> report on this
+module's test suite.
+
+ ---------------------------- ------ ------ ------ ------ ------ ------ ------
+ File stmt bran cond sub pod time total
+ ---------------------------- ------ ------ ------ ------ ------ ------ ------
+ Class/C3.pm 98.3 84.4 80.0 96.2 100.0 98.4 94.4
+ ---------------------------- ------ ------ ------ ------ ------ ------ ------
+ Total 98.3 84.4 80.0 96.2 100.0 98.4 94.4
+ ---------------------------- ------ ------ ------ ------ ------ ------ ------
+
=head1 SEE ALSO
=head2 The original Dylan paper
=back
+=head1 ACKNOWLEGEMENTS
+
+=over 4
+
+=item Thanks to Matt S. Trout for using this module in his module L<DBIx::Class>
+and finding many bugs and providing fixes.
+
+=item Thanks to Justin Guenther for making C<next::method> more robust by handling
+calls inside C<eval> and anon-subs.
+
+=item Thanks to Robert Norris for adding support for C<next::can> and
+C<maybe::next::method>.
+
+=back
+
=head1 AUTHOR
-stevan little, E<lt>stevan@iinteractive.comE<gt>
+Stevan Little, E<lt>stevan@iinteractive.comE<gt>
+
+Brandon L. Black, E<lt>blblack@gmail.comE<gt>
=head1 COPYRIGHT AND LICENSE
-Copyright 2005 by Infinity Interactive, Inc.
+Copyright 2005, 2006 by Infinity Interactive, Inc.
L<http://www.iinteractive.com>
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
-=cut
\ No newline at end of file
+=cut
projects / gitmo/Class-C3.git / blobdiff