summaryrefslogtreecommitdiff
path: root/Master/tlpkg/installer/perllib/base.pm
blob: 001914be4d388684ebc2c088bb12afce3445bb2f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
package base;

use strict 'vars';
use vars qw($VERSION);
$VERSION = '2.07';

# 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( ($fglob && *$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);

    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__};
            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;
        }
    }

    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 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