1 | package base;
|
---|
2 |
|
---|
3 | use strict 'vars';
|
---|
4 | use vars qw($VERSION);
|
---|
5 | $VERSION = '2.07';
|
---|
6 |
|
---|
7 | # constant.pm is slow
|
---|
8 | sub SUCCESS () { 1 }
|
---|
9 |
|
---|
10 | sub PUBLIC () { 2**0 }
|
---|
11 | sub PRIVATE () { 2**1 }
|
---|
12 | sub INHERITED () { 2**2 }
|
---|
13 | sub PROTECTED () { 2**3 }
|
---|
14 |
|
---|
15 |
|
---|
16 | my $Fattr = \%fields::attr;
|
---|
17 |
|
---|
18 | sub has_fields {
|
---|
19 | my($base) = shift;
|
---|
20 | my $fglob = ${"$base\::"}{FIELDS};
|
---|
21 | return( ($fglob && *$fglob{HASH}) ? 1 : 0 );
|
---|
22 | }
|
---|
23 |
|
---|
24 | sub has_version {
|
---|
25 | my($base) = shift;
|
---|
26 | my $vglob = ${$base.'::'}{VERSION};
|
---|
27 | return( ($vglob && *$vglob{SCALAR}) ? 1 : 0 );
|
---|
28 | }
|
---|
29 |
|
---|
30 | sub has_attr {
|
---|
31 | my($proto) = shift;
|
---|
32 | my($class) = ref $proto || $proto;
|
---|
33 | return exists $Fattr->{$class};
|
---|
34 | }
|
---|
35 |
|
---|
36 | sub get_attr {
|
---|
37 | $Fattr->{$_[0]} = [1] unless $Fattr->{$_[0]};
|
---|
38 | return $Fattr->{$_[0]};
|
---|
39 | }
|
---|
40 |
|
---|
41 | if ($] < 5.009) {
|
---|
42 | *get_fields = sub {
|
---|
43 | # Shut up a possible typo warning.
|
---|
44 | () = \%{$_[0].'::FIELDS'};
|
---|
45 | my $f = \%{$_[0].'::FIELDS'};
|
---|
46 |
|
---|
47 | # should be centralized in fields? perhaps
|
---|
48 | # fields::mk_FIELDS_be_OK. Peh. As long as %{ $package . '::FIELDS' }
|
---|
49 | # is used here anyway, it doesn't matter.
|
---|
50 | bless $f, 'pseudohash' if (ref($f) ne 'pseudohash');
|
---|
51 |
|
---|
52 | return $f;
|
---|
53 | }
|
---|
54 | }
|
---|
55 | else {
|
---|
56 | *get_fields = sub {
|
---|
57 | # Shut up a possible typo warning.
|
---|
58 | () = \%{$_[0].'::FIELDS'};
|
---|
59 | return \%{$_[0].'::FIELDS'};
|
---|
60 | }
|
---|
61 | }
|
---|
62 |
|
---|
63 | sub import {
|
---|
64 | my $class = shift;
|
---|
65 |
|
---|
66 | return SUCCESS unless @_;
|
---|
67 |
|
---|
68 | # List of base classes from which we will inherit %FIELDS.
|
---|
69 | my $fields_base;
|
---|
70 |
|
---|
71 | my $inheritor = caller(0);
|
---|
72 |
|
---|
73 | foreach my $base (@_) {
|
---|
74 | next if $inheritor->isa($base);
|
---|
75 |
|
---|
76 | if (has_version($base)) {
|
---|
77 | ${$base.'::VERSION'} = '-1, set by base.pm'
|
---|
78 | unless defined ${$base.'::VERSION'};
|
---|
79 | }
|
---|
80 | else {
|
---|
81 | local $SIG{__DIE__};
|
---|
82 | eval "require $base";
|
---|
83 | # Only ignore "Can't locate" errors from our eval require.
|
---|
84 | # Other fatal errors (syntax etc) must be reported.
|
---|
85 | die if $@ && $@ !~ /^Can't locate .*? at \(eval /;
|
---|
86 | unless (%{"$base\::"}) {
|
---|
87 | require Carp;
|
---|
88 | Carp::croak(<<ERROR);
|
---|
89 | Base class package "$base" is empty.
|
---|
90 | (Perhaps you need to 'use' the module which defines that package first.)
|
---|
91 | ERROR
|
---|
92 |
|
---|
93 | }
|
---|
94 | ${$base.'::VERSION'} = "-1, set by base.pm"
|
---|
95 | unless defined ${$base.'::VERSION'};
|
---|
96 | }
|
---|
97 | push @{"$inheritor\::ISA"}, $base;
|
---|
98 |
|
---|
99 | if ( has_fields($base) || has_attr($base) ) {
|
---|
100 | # No multiple fields inheritence *suck*
|
---|
101 | if ($fields_base) {
|
---|
102 | require Carp;
|
---|
103 | Carp::croak("Can't multiply inherit %FIELDS");
|
---|
104 | } else {
|
---|
105 | $fields_base = $base;
|
---|
106 | }
|
---|
107 | }
|
---|
108 | }
|
---|
109 |
|
---|
110 | if( defined $fields_base ) {
|
---|
111 | inherit_fields($inheritor, $fields_base);
|
---|
112 | }
|
---|
113 | }
|
---|
114 |
|
---|
115 |
|
---|
116 | sub inherit_fields {
|
---|
117 | my($derived, $base) = @_;
|
---|
118 |
|
---|
119 | return SUCCESS unless $base;
|
---|
120 |
|
---|
121 | my $battr = get_attr($base);
|
---|
122 | my $dattr = get_attr($derived);
|
---|
123 | my $dfields = get_fields($derived);
|
---|
124 | my $bfields = get_fields($base);
|
---|
125 |
|
---|
126 | $dattr->[0] = @$battr;
|
---|
127 |
|
---|
128 | if( keys %$dfields ) {
|
---|
129 | warn "$derived is inheriting from $base but already has its own ".
|
---|
130 | "fields!\n".
|
---|
131 | "This will cause problems.\n".
|
---|
132 | "Be sure you use base BEFORE declaring fields\n";
|
---|
133 | }
|
---|
134 |
|
---|
135 | # Iterate through the base's fields adding all the non-private
|
---|
136 | # ones to the derived class. Hang on to the original attribute
|
---|
137 | # (Public, Private, etc...) and add Inherited.
|
---|
138 | # This is all too complicated to do efficiently with add_fields().
|
---|
139 | while (my($k,$v) = each %$bfields) {
|
---|
140 | my $fno;
|
---|
141 | if ($fno = $dfields->{$k} and $fno != $v) {
|
---|
142 | require Carp;
|
---|
143 | Carp::croak ("Inherited %FIELDS can't override existing %FIELDS");
|
---|
144 | }
|
---|
145 |
|
---|
146 | if( $battr->[$v] & PRIVATE ) {
|
---|
147 | $dattr->[$v] = PRIVATE | INHERITED;
|
---|
148 | }
|
---|
149 | else {
|
---|
150 | $dattr->[$v] = INHERITED | $battr->[$v];
|
---|
151 | $dfields->{$k} = $v;
|
---|
152 | }
|
---|
153 | }
|
---|
154 |
|
---|
155 | foreach my $idx (1..$#{$battr}) {
|
---|
156 | next if defined $dattr->[$idx];
|
---|
157 | $dattr->[$idx] = $battr->[$idx] & INHERITED;
|
---|
158 | }
|
---|
159 | }
|
---|
160 |
|
---|
161 |
|
---|
162 | 1;
|
---|
163 |
|
---|
164 | __END__
|
---|
165 |
|
---|
166 | =head1 NAME
|
---|
167 |
|
---|
168 | base - Establish IS-A relationship with base classes at compile time
|
---|
169 |
|
---|
170 | =head1 SYNOPSIS
|
---|
171 |
|
---|
172 | package Baz;
|
---|
173 | use base qw(Foo Bar);
|
---|
174 |
|
---|
175 | =head1 DESCRIPTION
|
---|
176 |
|
---|
177 | Allows you to both load one or more modules, while setting up inheritance from
|
---|
178 | those modules at the same time. Roughly similar in effect to
|
---|
179 |
|
---|
180 | package Baz;
|
---|
181 | BEGIN {
|
---|
182 | require Foo;
|
---|
183 | require Bar;
|
---|
184 | push @ISA, qw(Foo Bar);
|
---|
185 | }
|
---|
186 |
|
---|
187 | If any of the listed modules are not loaded yet, I<base> silently attempts to
|
---|
188 | C<require> them (and silently continues if the C<require> failed). Whether to
|
---|
189 | C<require> a base class module is determined by the absence of a global variable
|
---|
190 | $VERSION in the base package. If $VERSION is not detected even after loading
|
---|
191 | it, <base> will define $VERSION in the base package, setting it to the string
|
---|
192 | C<-1, set by base.pm>.
|
---|
193 |
|
---|
194 | Will also initialize the fields if one of the base classes has it.
|
---|
195 | Multiple inheritence of fields is B<NOT> supported, if two or more
|
---|
196 | base classes each have inheritable fields the 'base' pragma will
|
---|
197 | croak. See L<fields>, L<public> and L<protected> for a description of
|
---|
198 | this feature.
|
---|
199 |
|
---|
200 | =head1 DIAGNOSTICS
|
---|
201 |
|
---|
202 | =over 4
|
---|
203 |
|
---|
204 | =item Base class package "%s" is empty.
|
---|
205 |
|
---|
206 | base.pm was unable to require the base package, because it was not
|
---|
207 | found in your path.
|
---|
208 |
|
---|
209 | =back
|
---|
210 |
|
---|
211 | =head1 HISTORY
|
---|
212 |
|
---|
213 | This module was introduced with Perl 5.004_04.
|
---|
214 |
|
---|
215 |
|
---|
216 | =head1 CAVEATS
|
---|
217 |
|
---|
218 | Due to the limitations of the implementation, you must use
|
---|
219 | base I<before> you declare any of your own fields.
|
---|
220 |
|
---|
221 |
|
---|
222 | =head1 SEE ALSO
|
---|
223 |
|
---|
224 | L<fields>
|
---|
225 |
|
---|
226 | =cut
|
---|