X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FClass%2FC3.pm;h=5c624222f79012eba9bf1a2ce7c83397db6efeaa;hb=ecb0388de108f3f6fe103a3ca4f6e28e26892a70;hp=3768c47c36974a382d9aad7001baf8dfbaddcae9;hpb=d401eda1e68a148b69c4e4992de7814fcaa44225;p=gitmo%2FClass-C3.git diff --git a/lib/Class/C3.pm b/lib/Class/C3.pm index 3768c47..5c62422 100644 --- a/lib/Class/C3.pm +++ b/lib/Class/C3.pm @@ -4,155 +4,18 @@ package Class::C3; use strict; use warnings; -use Scalar::Util 'blessed'; - -our $VERSION = '0.02'; - -# this is our global stash of both -# MRO's and method dispatch tables -# the structure basically looks like -# this: -# -# $MRO{$class} = { -# MRO => [ ], -# methods => { -# orig => , -# code => \& -# } -# } -# -my %MRO; - -# use this for debugging ... -sub _dump_MRO_table { %MRO } - -our $TURN_OFF_C3 = 0; - -sub import { - my $class = caller(); - # skip if the caller is main:: - # since that is clearly not relevant - return if $class eq 'main'; - return if $TURN_OFF_C3; - # make a note to calculate $class - # during INIT phase - $MRO{$class} = undef; -} - -## initializers - -# NOTE: -# this will not run under the following -# conditions: -# - mod_perl -# - require Class::C3; -# - eval "use Class::C3" -# in all those cases, you need to call -# the initialize() function manually -INIT { initialize() } - -sub initialize { - # why bother if we don't have anything ... - return unless keys %MRO; - _calculate_method_dispatch_tables(); - _apply_method_dispatch_tables(); -} - -## functions for applying C3 to classes - -sub _calculate_method_dispatch_tables { - foreach my $class (keys %MRO) { - _calculate_method_dispatch_table($class); - } -} - -sub _calculate_method_dispatch_table { - my $class = shift; - no strict 'refs'; - my @MRO = calculateMRO($class); - $MRO{$class} = { MRO => \@MRO }; - 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]) { - 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; -} - -sub _apply_method_dispatch_tables { - foreach my $class (keys %MRO) { - _apply_method_dispatch_table($class); - } -} - -sub _apply_method_dispatch_table { - my $class = shift; - no strict 'refs'; - foreach my $method (keys %{$MRO{$class}->{methods}}) { - *{"${class}::$method"} = $MRO{$class}->{methods}->{$method}->{code}; - } -} - -## functions for calculating C3 MRO - -# this function is a perl-port of the -# python code on this page: -# http://www.python.org/2.3/mro.html -sub _merge { - my (@seqs) = @_; - my @res; - while (1) { - # remove all empty seqences - my @nonemptyseqs = (map { (@{$_} ? $_ : ()) } @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; +our $VERSION = '0.15'; + +BEGIN { + eval { require Class::C3::XS }; + if($@) { + eval { require Class::C3::PurePerl }; + if($@) { + die 'Could not load Class::C3::XS or Class::C3::PurePerl!'; } } } -sub calculateMRO { - my ($class) = @_; - 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 - ); -} - 1; __END__ @@ -191,6 +54,10 @@ Class::C3 - A pragma to use the C3 method resolution order algortihm # 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 @@ -201,9 +68,8 @@ Class::C3 - A pragma to use the C3 method resolution order algortihm =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? @@ -233,11 +99,11 @@ the L section. =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. 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 is +called, this module calculates the MRO of all the classes which called C. 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 @@ -269,25 +135,106 @@ Given a C<$class> this will return an array of class names in the proper C3 meth =item B -This can be used to initalize the C3 method dispatch tables. You need to call this if you are running -under mod_perl, or in any other environment which does not run the INIT phase of the perl compiler. +This B to initalize the C3 method dispatch tables, this module B if +you do not do this. It is advised to do this as soon as possible B 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 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 folks). The simplest solution of course is to define +your own INIT method which calls this function. NOTE: -This can B be used to re-load the dispatch tables for all classes. This is because it does not first -return the classes to their virginal state, which would need to happen in order for the dispatch tables -to be properly reloaded. + +If C detects that C has already been executed, it will L and +clear the MRO cache first. + +=item B + +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 + +This is an alias for L above. =back -=head1 CAVEATS +=head1 METHOD REDISPATCHING -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. +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 or C which will re-dispatch the +method along the C3 linearization. This is best show with an examples. -That said, it is the authors intention to make this into a completely usable and production stable -module if possible. Time will tell. + # a classic diamond MI pattern ... + + / \ + + \ / + + + 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 +call (this is unlike C and C 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 behaves as well). + +The next thing to keep in mind is that you will need to pass all arguments to C it can +not automatically use the current C<@_>. + +If C cannot find a next method to re-dispatch the call to, it will throw an exception. +You can use C to see if C will succeed before you call it like so: + + $self->next::method(@_) if $self->next::can; + +Additionally, you can use C 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, see below for those. + +=head1 CAVEATS -And now, onto the caveats. +This module used to be labeled as I, however it has now been pretty heavily tested by +the good folks over at L and I am confident this module is perfectly usable for +whatever your needs might be. + +But there are still caveats, so here goes ... =over 4 @@ -295,46 +242,60 @@ And now, onto the caveats. The idea of C 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 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 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 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 +in order to recalulate B method dispatch tables. See the C documentation and an example +in F 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. - -=back +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 for any +changes you make to take effect. -=head1 TODO +=item Calling C from methods defined outside the class -=over 4 +There is an edge case when using C 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: -=item More tests + *Foo::foo = sub { (shift)->next::method(@_) }; -You can never have enough tests :) +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 as you might expect. Since C +uses C to find the name of the method it was called in, it will fail in this case. -I need to convert the other MRO and class-precendence-list related tests from the Perl6-MetaModel (see link -in L). In addition, I need to add some method checks to these tests as well. +But fear not, there is a simple solution. The module C 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(@_) }; -=item call-next-method / NEXT:: / 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. -I am contemplating some kind of psudeo-package which can dispatch to the next most relevant method in the -MRO. This should not be too hard to implement when the time comes. +=back -=item recalculateMRO +=head1 CODE COVERAGE -This being Perl, it would be remiss of me to force people to close thier classes at runtime. So I need to -develop a means for recalculating the MRO for a given class. +I use B to test the code coverage of my tests, below is the B report on this +module's test suite. -=back + ---------------------------- ------ ------ ------ ------ ------ ------ ------ + 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 @@ -382,17 +343,34 @@ develop a means for recalculating the MRO for a given class. =back +=head1 ACKNOWLEGEMENTS + +=over 4 + +=item Thanks to Matt S. Trout for using this module in his module L +and finding many bugs and providing fixes. + +=item Thanks to Justin Guenther for making C more robust by handling +calls inside C and anon-subs. + +=item Thanks to Robert Norris for adding support for C and +C. + +=back + =head1 AUTHOR Stevan Little, Estevan@iinteractive.comE +Brandon L. Black, Eblblack@gmail.comE + =head1 COPYRIGHT AND LICENSE -Copyright 2005 by Infinity Interactive, Inc. +Copyright 2005, 2006 by Infinity Interactive, Inc. L 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