-=head1 NAME
-
-base - Establish IS-A relationship with base class at compile time
-
-=head1 SYNOPSIS
-
- package Baz;
- use base qw(Foo Bar);
+package base;
-=head1 DESCRIPTION
+use strict 'vars';
+use vars qw($VERSION);
+$VERSION = '2.06';
-Roughly similar in effect to
+# constant.pm is slow
+sub SUCCESS () { 1 }
- BEGIN {
- require Foo;
- require Bar;
- push @ISA, qw(Foo Bar);
- }
+sub PUBLIC () { 2**0 }
+sub PRIVATE () { 2**1 }
+sub INHERITED () { 2**2 }
+sub PROTECTED () { 2**3 }
-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.
-When strict 'vars' is in scope I<base> also let you assign to @ISA
-without having to declare @ISA with the 'vars' pragma first.
+my $Fattr = \%fields::attr;
-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 $VERSION in the base package, setting it to the string
-C<-1, defined by base.pm>.
+sub has_fields {
+ my($base) = shift;
+ my $fglob = ${"$base\::"}{FIELDS};
+ return( ($fglob && *$fglob{HASH}) ? 1 : 0 );
+}
-=head1 HISTORY
+sub has_version {
+ my($base) = shift;
+ my $vglob = ${$base.'::'}{VERSION};
+ return( ($vglob && *$vglob{SCALAR}) ? 1 : 0 );
+}
-This module was introduced with Perl 5.004_04.
+sub has_attr {
+ my($proto) = shift;
+ my($class) = ref $proto || $proto;
+ return exists $Fattr->{$class};
+}
-=head1 SEE ALSO
+sub get_attr {
+ $Fattr->{$_[0]} = [1] unless $Fattr->{$_[0]};
+ return $Fattr->{$_[0]};
+}
-L<fields>
+if ($] < 5.009) {
+ *get_fields = sub {
+ # Shut up a possible typo warning.
+ () = \%{$_[0].'::FIELDS'};
+ my $f = \%{$_[0].'::FIELDS'};
-=cut
+ # 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');
-package base;
-use vars qw($VERSION);
-$VERSION = "1.00";
+ 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;
- 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};
- }
+ my $inheritor = caller(0);
- # A simple test like (defined %{"$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}) {
+ foreach my $base (@_) {
+ next if $inheritor->isa($base);
+
+ if (has_version($base)) {
+ ${$base.'::VERSION'} = '-1, set by base.pm'
+ unless defined ${$base.'::VERSION'};
+ }
+ else {
+ local $SIG{__DIE__} = 'IGNORE';
+ 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 (%{"$base\::"}) {
+ require Carp;
+ Carp::croak(<<ERROR);
+Base class package "$base" is empty.
+ (Perhaps you need to 'use' the module which defines that package first.)
+ERROR
+
+ }
+ ${$base.'::VERSION'} = "-1, set by base.pm"
+ unless defined ${$base.'::VERSION'};
+ }
+ push @{"$inheritor\::ISA"}, $base;
+
+ if ( has_fields($base) || has_attr($base) ) {
+ # No multiple fields inheritence *suck*
if ($fields_base) {
require Carp;
Carp::croak("Can't multiply inherit %FIELDS");
} else {
$fields_base = $base;
}
+ }
+ }
+
+ 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 %$dfields ) {
+ warn "$derived is inheriting from $base but already has its own ".
+ "fields!\n".
+ "This will cause problems.\n".
+ "Be sure you use base BEFORE declaring fields\n";
+ }
+
+ # Iterate through the base's fields adding all the non-private
+ # ones to the derived class. Hang on to the original attribute
+ # (Public, Private, etc...) and add Inherited.
+ # This is all too complicated to do efficiently with add_fields().
+ while (my($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;
+ }
}
- my $pkg = caller(0);
- push @{"$pkg\::ISA"}, @_;
- if ($fields_base) {
- require fields;
- fields::inherit($pkg, $fields_base);
+
+ unless( keys %$bfields ) {
+ foreach my $idx (1..$#{$battr}) {
+ $dattr->[$idx] = $battr->[$idx] & INHERITED;
+ }
}
}
+
1;
+
+__END__
+
+=head1 NAME
+
+base - Establish IS-A relationship with base classes at compile time
+
+=head1 SYNOPSIS
+
+ package Baz;
+ use base qw(Foo Bar);
+
+=head1 DESCRIPTION
+
+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);
+ }
+
+If any of the listed modules are not loaded yet, I<base> silently attempts to
+C<require> them (and silently continues if the C<require> failed). Whether to
+C<require> a base class module is determined by the absence of a global variable
+$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, set by base.pm>.
+
+Will also initialize the fields if one of the base classes has it.
+Multiple inheritence 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.
+
+=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.
+
+=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.
+
+
+=head1 SEE ALSO
+
+L<fields>
+
+=cut
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