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perl5/
base.pm/
/
use 5.008; package base;
use strict 'vars'; use vars qw($VERSION); $VERSION = '2.26'; $VERSION =~ tr/_//d;
# simplest way to avoid indexing of the package: no package statement sub base::__inc::unhook { @INC = grep !(ref eq 'CODE' && $_ == $_[0]), @INC } # instance is blessed array of coderefs to be removed from @INC at scope exit sub base::__inc::scope_guard::DESTROY { base::__inc::unhook $_ for @{$_[0]} }
# constant.pm is slow sub SUCCESS () { 1 }
sub PUBLIC () { 2**0 } sub PRIVATE () { 2**1 } sub INHERITED () { 2**2 } sub PROTECTED () { 2**3 }
if ($] < 5.009) { *get_fields = sub { # Shut up a possible typo warning. () = \%{$_[0].'::FIELDS'}; my $f = \%{$_[0].'::FIELDS'};
# should be centralized in fields? perhaps # fields::mk_FIELDS_be_OK. Peh. As long as %{ $package . '::FIELDS' } # is used here anyway, it doesn't matter. bless $f, 'pseudohash' if (ref($f) ne 'pseudohash');
return $f; } } else { *get_fields = sub { # Shut up a possible typo warning. () = \%{$_[0].'::FIELDS'}; return \%{$_[0].'::FIELDS'}; } }
# List of base classes from which we will inherit %FIELDS. my $fields_base;
my $inheritor = caller(0);
my @bases; foreach my $base (@_) { if ( $inheritor eq $base ) { warn "Class '$inheritor' tried to inherit from itself\n"; }
next if grep $_->isa($base), ($inheritor, @bases);
# Following blocks help isolate $SIG{__DIE__} and @INC changes { my $sigdie; { local $SIG{__DIE__}; my $fn = _module_to_filename($base); my $dot_hidden; eval { my $guard; if ($INC[-1] eq '.' && %{"$base\::"}) { # So: the package already exists => this an optional load # And: there is a dot at the end of @INC => we want to hide it # However: we only want to hide it during our *own* require() # (i.e. without affecting nested require()s). # So we add a hook to @INC whose job is to hide the dot, but which # first checks checks the callstack depth, because within nested # require()s the callstack is deeper. # Since CORE::GLOBAL::require makes it unknowable in advance what # the exact relevant callstack depth will be, we have to record it # inside a hook. So we put another hook just for that at the front # of @INC, where it's guaranteed to run -- immediately. # The dot-hiding hook does its job by sitting directly in front of # the dot and removing itself from @INC when reached. This causes # the dot to move up one index in @INC, causing the loop inside # pp_require() to skip it. # Loaded coded may disturb this precise arrangement, but that's OK # because the hook is inert by that time. It is only active during # the top-level require(), when @INC is in our control. The only # possible gotcha is if other hooks already in @INC modify @INC in # some way during that initial require(). # Note that this jiggery hookery works just fine recursively: if # a module loaded via base.pm uses base.pm itself, there will be # one pair of hooks in @INC per base::import call frame, but the # pairs from different nestings do not interfere with each other. my $lvl; unshift @INC, sub { return if defined $lvl; 1 while defined caller ++$lvl; () }; splice @INC, -1, 0, sub { return if defined caller $lvl; ++$dot_hidden, &base::__inc::unhook; () }; $guard = bless [ @INC[0,-2] ], 'base::__inc::scope_guard'; } require $fn }; if ($dot_hidden && (my @fn = grep -e && !( -d _ || -b _ ), $fn.'c', $fn)) { require Carp; Carp::croak(<<ERROR); Base class package "$base" is not empty but "$fn[0]" exists in the current directory. To help avoid security issues, base.pm now refuses to load optional modules from the current working directory when it is the last entry in \@INC. If your software worked on previous versions of Perl, the best solution is to use FindBin to detect the path properly and to add that path to \@INC. As a last resort, you can re-enable looking in the current working directory by adding "use lib '.'" to your code. ERROR } # Only ignore "Can't locate" errors from our eval require. # Other fatal errors (syntax etc) must be reported. # # changing the check here is fragile - if the check # here isn't catching every error you want, you should # probably be using parent.pm, which doesn't try to # guess whether require is needed or failed, # see [perl #118561] die if $@ && $@ !~ /^Can't locate \Q$fn\E .*? at .* line [0-9]+(?:, <[^>]*> (?:line|chunk) [0-9]+)?\.\n\z/s || $@ =~ /Compilation failed in require at .* line [0-9]+(?:, <[^>]*> (?:line|chunk) [0-9]+)?\.\n\z/; unless (%{"$base\::"}) { require Carp; local $" = " "; Carp::croak(<<ERROR); Base class package "$base" is empty. (Perhaps you need to 'use' the module which defines that package first, or make that module available in \@INC (\@INC contains: @INC). ERROR } $sigdie = $SIG{__DIE__} || undef; } # Make sure a global $SIG{__DIE__} makes it out of the localization. $SIG{__DIE__} = $sigdie if defined $sigdie; } push @bases, $base;
if ( has_fields($base) || has_attr($base) ) { # No multiple fields inheritance *suck* if ($fields_base) { require Carp; Carp::croak("Can't multiply inherit fields"); } else { $fields_base = $base; } } } # Save this until the end so it's all or nothing if the above loop croaks. push @{"$inheritor\::ISA"}, @bases;
if( defined $fields_base ) { inherit_fields($inheritor, $fields_base); } }
sub inherit_fields { my($derived, $base) = @_;
return SUCCESS unless $base;
my $battr = get_attr($base); my $dattr = get_attr($derived); my $dfields = get_fields($derived); my $bfields = get_fields($base);
$dattr->[0] = @$battr;
if( keys %$dfields ) { warn <<"END"; $derived is inheriting from $base but already has its own fields! This will cause problems. Be sure you use base BEFORE declaring fields. END
}
# Iterate through the base's fields adding all the non-private # ones to the derived class. Hang on to the original attribute # (Public, Private, etc...) and add Inherited. # This is all too complicated to do efficiently with add_fields(). while (my($k,$v) = each %$bfields) { my $fno; if ($fno = $dfields->{$k} and $fno != $v) { require Carp; Carp::croak ("Inherited fields can't override existing fields"); }
When C<base> tries to C<require> a module, it will not die if it cannot find the module's file, but will die on any other error. After all this, should your base class be empty, containing no symbols, C<base> will die. This is useful for inheriting from classes in the same file as yourself but where the filename does not match the base module name, like so:
# in Bar.pm package Foo; sub exclaim { "I can have such a thing?!" }
package Bar; use base "Foo";
There is no F<Foo.pm>, but because C<Foo> defines a symbol (the C<exclaim> subroutine), C<base> will not die when the C<require> fails to load F<Foo.pm>.
C<base> will also initialize the fields if one of the base classes has it. Multiple inheritance of fields is B<NOT> supported, if two or more base classes each have inheritable fields the 'base' pragma will croak. See L<fields> for a description of this feature.
The base class' C<import> method is B<not> called.
=head1 DIAGNOSTICS
=over 4
=item Base class package "%s" is empty.
base.pm was unable to require the base package, because it was not found in your path.
=item Class 'Foo' tried to inherit from itself
Attempting to inherit from yourself generates a warning.
package Foo; use base 'Foo';
=back
=head1 HISTORY
This module was introduced with Perl 5.004_04.
=head1 CAVEATS
Due to the limitations of the implementation, you must use base I<before> you declare any of your own fields.