+package base;
+
+use strict 'vars';
+use vars qw($VERSION);
+$VERSION = '2.14';
+$VERSION = eval $VERSION;
+
+# constant.pm is slow
+sub SUCCESS () { 1 }
+
+sub PUBLIC () { 2**0 }
+sub PRIVATE () { 2**1 }
+sub INHERITED () { 2**2 }
+sub PROTECTED () { 2**3 }
+
+
+my $Fattr = \%fields::attr;
+
+sub has_fields {
+ my($base) = shift;
+ my $fglob = ${"$base\::"}{FIELDS};
+ return( ($fglob && 'GLOB' eq ref($fglob) && *$fglob{HASH}) ? 1 : 0 );
+}
+
+sub has_version {
+ my($base) = shift;
+ my $vglob = ${$base.'::'}{VERSION};
+ return( ($vglob && *$vglob{SCALAR}) ? 1 : 0 );
+}
+
+sub has_attr {
+ my($proto) = shift;
+ my($class) = ref $proto || $proto;
+ return exists $Fattr->{$class};
+}
+
+sub get_attr {
+ $Fattr->{$_[0]} = [1] unless $Fattr->{$_[0]};
+ return $Fattr->{$_[0]};
+}
+
+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'};
+ }
+}
+
+sub import {
+ my $class = shift;
+
+ return SUCCESS unless @_;
+
+ # List of base classes from which we will inherit %FIELDS.
+ my $fields_base;
+
+ my $inheritor = caller(0);
+ my @isa_classes;
+
+ my @bases;
+ foreach my $base (@_) {
+ if ( $inheritor eq $base ) {
+ warn "Class '$inheritor' tried to inherit from itself\n";
+ }
+
+ next if grep $_->isa($base), ($inheritor, @bases);
+
+ if (has_version($base)) {
+ ${$base.'::VERSION'} = '-1, set by base.pm'
+ unless defined ${$base.'::VERSION'};
+ }
+ else {
+ my $sigdie;
+ {
+ local $SIG{__DIE__};
+ eval "require $base";
+ # Only ignore "Can't locate" errors from our eval require.
+ # Other fatal errors (syntax etc) must be reported.
+ die if $@ && $@ !~ /^Can't locate .*? at \(eval /;
+ 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;
+ ${$base.'::VERSION'} = "-1, set by base.pm"
+ unless defined ${$base.'::VERSION'};
+ }
+ 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"}, @isa_classes;
+
+ 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");
+ }
+
+ if( $battr->[$v] & PRIVATE ) {
+ $dattr->[$v] = PRIVATE | INHERITED;
+ }
+ else {
+ $dattr->[$v] = INHERITED | $battr->[$v];
+ $dfields->{$k} = $v;
+ }
+ }
+
+ foreach my $idx (1..$#{$battr}) {
+ next if defined $dattr->[$idx];
+ $dattr->[$idx] = $battr->[$idx] & INHERITED;
+ }
+}
+
+
+1;
+
+__END__
+
=head1 NAME
-base - Establish IS-A relationship with base class at compile time
+base - Establish an ISA relationship with base classes at compile time
=head1 SYNOPSIS
=head1 DESCRIPTION
-Roughly similar in effect to
+Unless you are using the C<fields> pragma, consider this module discouraged
+in favor of the lighter-weight C<parent>.
+Allows you to both load one or more modules, while setting up inheritance from
+those modules at the same time. Roughly similar in effect to
+
+ package Baz;
BEGIN {
- require Foo;
- require Bar;
- push @ISA, qw(Foo Bar);
+ require Foo;
+ require Bar;
+ push @ISA, qw(Foo Bar);
}
-Will also initialize the %FIELDS hash if one of the base classes has
-it. Multiple inheritance of %FIELDS is not supported. The 'base'
-pragma will croak if multiple base classes have a %FIELDS hash. See
-L<fields> for a description of this feature.
+C<base> employs some heuristics to determine if a module has already been
+loaded, if it has it doesn't try again. If C<base> tries to C<require> the
+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, it will die. This is useful for inheriting from classes in the same
+file as yourself, like so:
+
+ package Foo;
+ sub exclaim { "I can have such a thing?!" }
+
+ package Bar;
+ use base "Foo";
+
+If $VERSION is not detected even after loading it, <base> will define $VERSION
+in the base package, setting it to the string C<-1, set by base.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>,
+L<public> and L<protected> for a description of this feature.
+
+The base class' C<import> method is B<not> called.
+
+
+=head1 DIAGNOSTICS
-When strict 'vars' is in scope I<base> also let you assign to @ISA
-without having to declare @ISA with the 'vars' pragma first.
+=over 4
-If any of the base classes are not loaded yet, I<base> silently
-C<require>s them. Whether to C<require> a base class package is
-determined by the absence of a global $VERSION in the base package.
-If $VERSION is not detected even after loading it, <base> will
-define $VERSION in the base package, setting it to the string
-C<-1, defined by base.pm>.
+=item Base class package "%s" is empty.
+
+base.pm was unable to require the base package, because it was not
+found in your path.
+
+=item Class 'Foo' tried to inherit from itself
+
+Attempting to inherit from yourself generates a warning.
+
+ use Foo;
+ use base 'Foo';
+
+=back
=head1 HISTORY
This module was introduced with Perl 5.004_04.
-=head1 SEE ALSO
+=head1 CAVEATS
-L<fields>
-
-=cut
+Due to the limitations of the implementation, you must use
+base I<before> you declare any of your own fields.
-package base;
-use vars qw($VERSION);
-$VERSION = "1.00";
-sub import {
- my $class = shift;
- my $fields_base;
+=head1 SEE ALSO
- foreach my $base (@_) {
- unless (exists ${"$base\::"}{VERSION}) {
- eval "require $base";
- # Only ignore "Can't locate" errors from our eval require.
- # Other fatal errors (syntax etc) must be reported.
- die if $@ && $@ !~ /^Can't locate .*? at \(eval /;
- unless (defined %{"$base\::"}) {
- require Carp;
- Carp::croak("Base class package \"$base\" is empty.\n",
- "\t(Perhaps you need to 'use' the module ",
- "which defines that package first.)");
- }
- ${"$base\::VERSION"} = "-1, set by base.pm"
- unless exists ${"$base\::"}{VERSION};
- }
-
- # A simple test like (defined %{"$base\::FIELDS"}) will
- # sometimes produce typo warnings because it would create
- # the hash if it was not present before.
- my $fglob;
- if ($fglob = ${"$base\::"}{"FIELDS"} and *$fglob{HASH}) {
- if ($fields_base) {
- require Carp;
- Carp::croak("Can't multiply inherit %FIELDS");
- } else {
- $fields_base = $base;
- }
- }
- }
- my $pkg = caller(0);
- push @{"$pkg\::ISA"}, @_;
- if ($fields_base) {
- require fields;
- fields::inherit($pkg, $fields_base);
- }
-}
+L<fields>
-1;
+=cut
https://perl5.git.perl.org / perl5.git / blobdiff